U.S. patent application number 13/397753 was filed with the patent office on 2012-06-14 for method of making a fabric-creped absorbent cellulosic sheet.
This patent application is currently assigned to GEORGIA-PACIFIC CONSUMER PRODUCTS LP. Invention is credited to Steven L. Edwards, Stephen J. McCullough, Frank C. Murray, Guy H. Super.
Application Number | 20120145341 13/397753 |
Document ID | / |
Family ID | 37115628 |
Filed Date | 2012-06-14 |
United States Patent
Application |
20120145341 |
Kind Code |
A1 |
Super; Guy H. ; et
al. |
June 14, 2012 |
Method of Making a Fabric-Creped Absorbent Cellulosic Sheet
Abstract
A method of making a fabric-creped absorbent cellulosic sheet
includes applying a jet of papermaking furnish to a forming wire,
the jet having a jet velocity and the forming wire moving at a
forming wire velocity. The papermaking furnish is compactively
dewatered to form a nascent web. The nascent web is applied to a
transfer surface that is moving at a transfer surface speed. The
nascent web is fabric-creped from the transfer surface at a
consistency of from about 30 to about 60 percent utilizing a
creping fabric that is traveling at a fabric-creping speed, the
fabric-creping speed being slower than the transfer surface speed,
and the fabric-creping step occurring under pressure in a fabric
creping nip defined between the transfer surface and the creping
fabric, such that the nascent web is creped from the transfer
surface and redistributed on the creping fabric to form a creped
web. The creped web is dried. The jet/wire velocity delta and the
fabric-creping step are controlled such that the dry machine
direction to cross-machine direction (MD/CD) tensile ratio of the
dried web is about at most 1.5.
Inventors: |
Super; Guy H.; (Menasha,
WI) ; Edwards; Steven L.; (Fremont, WI) ;
McCullough; Stephen J.; (Mount Calvary, WI) ; Murray;
Frank C.; (Marietta, GA) |
Assignee: |
GEORGIA-PACIFIC CONSUMER PRODUCTS
LP
Atlanta
GA
|
Family ID: |
37115628 |
Appl. No.: |
13/397753 |
Filed: |
February 16, 2012 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
12804210 |
Jul 16, 2010 |
8152958 |
|
|
13397753 |
|
|
|
|
11108375 |
Apr 18, 2005 |
7789995 |
|
|
12804210 |
|
|
|
|
10679862 |
Oct 6, 2003 |
7399378 |
|
|
11108375 |
|
|
|
|
60416666 |
Oct 7, 2002 |
|
|
|
Current U.S.
Class: |
162/111 |
Current CPC
Class: |
A47K 10/02 20130101;
Y10T 428/24455 20150115; D21H 25/005 20130101; D21H 27/02 20130101;
B31F 1/16 20130101; D21F 11/006 20130101; D21H 27/40 20130101; D21H
27/005 20130101; D21H 21/20 20130101; B31F 1/126 20130101; D21H
27/007 20130101; D21H 11/14 20130101 |
Class at
Publication: |
162/111 |
International
Class: |
D21F 11/00 20060101
D21F011/00 |
Claims
1. A method of making a fabric-creped absorbent cellulosic sheet,
the method comprising: (a) applying a jet of papermaking furnish to
a forming wire, the jet having a jet velocity and the forming wire
moving at a forming wire velocity, the difference between the jet
velocity and the forming wire velocity being referred to as the
jet/wire velocity delta; (b) compactively dewatering the
papermaking furnish to form a nascent web; (c) applying the nascent
web to a transfer surface that is moving at a transfer surface
speed; (d) fabric-creping the nascent web from the transfer surface
at a consistency of from about 30 to about 60 percent utilizing a
creping fabric that is traveling at a fabric-creping speed, the
fabric-creping speed being slower than the transfer surface speed,
the fabric-creping step occurring under pressure in a fabric
creping nip defined between the transfer surface and the creping
fabric, such that the nascent web is creped from the transfer
surface and redistributed on the creping fabric to form a creped
web; (e) drying the creped web; and (f) controlling the jet/wire
velocity delta and the fabric-creping step, such that the dry
machine direction to cross-machine direction (MD/CD) tensile ratio
of the dried web is about at most 1.5.
2. The method according to claim 1, further including controlling
the jet/wire velocity delta and the fabric-creping step such that
the dry MD/CD tensile ratio of the dried web is about at most
1.
3. The method according to claim 1, further including controlling
the jet/wire velocity delta and the fabric-creping step such that
the dry MD/CD tensile ratio of the dried web is about at most
0.75.
4. The method according to claim 1, further including controlling
the jet/wire velocity delta and the fabric-creping step such that
the dry MD/CD tensile ratio of the dried web is about at most
0.5.
5. The method according to claim 1, further including controlling
the jet/wire velocity delta to be greater than about 300 fpm.
6. The method according to claim 1, further including controlling
the jet/wire velocity delta to be greater than about 350 fpm.
7. The method according to claim 1, further including controlling
the jet/wire velocity delta to be less than about 50 fpm.
8. The method according to claim 1, further including controlling
the jet/wire velocity delta to be less than 0 fpm, such that the
forming wire velocity exceeds the jet velocity.
9. The method according to claim 1, wherein the creped web has a
reticulum with a plurality of interconnected regions of different
local basis weights including at least (i) a plurality of fiber
enriched regions of a high local basis weight, interconnected by
way of (ii) a plurality of lower local basis weight linking
regions.
10. A method of making a fabric-creped absorbent cellulosic sheet,
the method comprising: (a) supplying a jet of papermaking furnish
to a forming wire, the jet having a jet velocity and the forming
wire moving at a forming wire velocity, the difference between the
jet velocity and the forming wire velocity being referred to as the
jet/wire velocity delta; (b) compactively dewatering the
papermaking furnish to form a nascent web; (c) applying the nascent
web to a transfer surface that is moving at a transfer surface
speed; (d) fabric-creping the nascent web from the transfer surface
at a consistency of from about 30 to about 60 percent utilizing a
creping fabric that is traveling at a fabric-creping speed, the
fabric-creping speed being slower than the transfer surface speed,
the fabric-creping step occurring under pressure in a fabric
creping nip defined between the transfer surface and the creping
fabric, such that the nascent web is creped from the transfer
surface and redistributed on the creping fabric to form a creped
web; (e) drying the creped web; and (f) controlling the jet/wire
velocity delta and the fabric-creping step, such that the dry
machine direction to cross-machine direction (MD/CD) tensile ratio
of the dried web is about at most 1.5, with the proviso that the
jet/wire velocity delta is one of (i) negative and (ii) greater
than about 350 fpm.
11. The method according to claim 10, wherein the jet/wire velocity
delta is greater than about 400 fpm.
12. The method according to claim 10, wherein the jet/wire velocity
delta is greater than about 450 fpm.
13. The method according to claim 10, wherein the creped web has a
reticulum with a plurality of interconnected regions of different
local basis weights including at least (i) a plurality of fiber
enriched regions of a high local basis weight, interconnected by
way of (ii) a plurality of lower local basis weight linking
regions.
Description
CLAIM FOR PRIORITY AND TECHNICAL FIELD
[0001] This application is a continuation application of U.S.
patent application Ser. No. 12/804,210, filed on Jul. 16, 2010,
which is a divisional of U.S. patent application Ser. No.
11/108,375, entitled "Fabric Crepe/Draw Process for Producing
Absorbent Sheet", now U.S. Pat. No. 7,789,995. U.S. patent
application Ser. No. 11/108,375 is a continuation-in-part of
copending U.S. patent application Ser. No. 10/679,862 entitled
"Fabric Crepe Process for Making Absorbent Sheet", filed on Oct. 6,
2003, now U.S. Pat. No. 7,399,378. Further, this application claims
the benefit of the filing date of U.S. Provisional Patent
Application No. 60/416,666, filed Oct. 7, 2002. This application is
directed, in part, to a process wherein a web is compactively
dewatered, creped into a creping fabric and drawn to expand the
dried web. The priorities of U.S. patent application Ser. No.
11/108,375, U.S. patent application Ser. No. 10/679,862 and U.S.
Provisional Patent Application No. 60/416,666 are hereby claimed
and their disclosures are incorporated herein in their
entireties.
BACKGROUND
[0002] Methods of making paper tissue, towel, and the like, are
well known, including various features such as Yankee drying,
throughdrying, fabric creping, dry creping, wet creping, and so
forth. Conventional wet pressing processes have certain advantages
over conventional through-air drying (TAD) processes including: (1)
lower energy costs associated with the mechanical removal of water
rather than transpiration drying with hot air, and (2) higher
production speeds, which are more readily achieved with processes
that utilize wet pressing to form a web. On the other hand,
through-air drying processing has been widely adopted from new
capital investment, particularly, for the production of soft,
bulky, premium quality tissue and towel products.
[0003] Fabric creping has been employed in connection with
papermaking processes that include mechanical or compactive
dewatering of the paper web as a means to influence product
properties. See U.S. Pat. Nos. 4,689,119 and 4,551,199 to Weldon;
U.S. Pat. Nos. 4,849,054 and 4,834,838 to Klowak; and U.S. Pat. No.
6,287,426 to Edwards et al. Operation of fabric creping processes
has been hampered by the difficulty of effectively transferring a
web of high or intermediate consistency to a dryer. Note also U.S.
Pat. No. 6,350,349 to Hermans et al., which discloses wet transfer
of a web from a rotating transfer surface to a fabric. Further
United States Patents relating to fabric creping more generally
include the following: U.S. Pat. Nos. 4,834,838; 4,482,429 and
4,445,638, as well as No. 4,440,597 to Wells et al.
[0004] In connection with papermaking processes, fabric molding has
also been employed as a means to provide texture and bulk. In this
respect, there is seen in U.S. Pat. No. 6,610,173 to Lindsey et al.
a method of imprinting a paper web during a wet pressing event
which results in asymmetrical protrusions corresponding to the
deflection conduits of a deflection member. The '173 patent reports
that a differential velocity transfer during a pressing event
serves to improve the molding and imprinting of a web with a
deflection member. The tissue webs produced are reported as having
particular sets of physical and geometrical properties, such as a
pattern densified network and a repeating pattern of protrusions
having asymmetrical structures. With respect to wet-molding of a
web using textured fabrics, see, also, the following U.S. Pat. Nos.
6,017,417 and 5,672,248 both to Wendt et al.; U.S. Pat. Nos.
5,508,818 and 5,510,002 to Hermans et al. and U.S. Pat. No.
4,637,859 to Trokhan. With respect to the use of fabrics used to
impart texture to a mostly dry sheet, see U.S. Pat. No. 6,585,855
to Drew et al., as well as United States Patent Application
Publication No. 2003/0000664, now U.S. Pat. No. 6,607,638.
[0005] Throughdried, creped products are disclosed in the following
patents: U.S. Pat. No. 3,994,771 to Morgan, Jr. et al.; U.S. Pat.
No. 4,102,737 to Morton; and U.S. Pat. No. 4,529,480 to Trokhan.
The processes described in these patents comprise, very generally,
forming a web on a foraminous support, thermally pre-drying the
web, applying the web to a Yankee dryer with a nip defined, in
part, by an impression fabric, and creping the product from the
Yankee dryer. A relatively permeable web is typically required,
making it difficult to employ recycle furnish at levels which may
be desired. Transfer to the Yankee typically takes place at web
consistencies of from about 60% to about 70%. See also, U.S. Pat.
No. 6,187,137 to Druecke et al. As to the application of a vacuum
while the web is in a fabric, the following are noted: U.S. Pat.
No. 5,411,636 to Hermans et al.; U.S. Pat. No. 5,492,598 to Hermans
et al.; U.S. Pat. No. 5,505,818 to Hermans et al.; U.S. Pat. No.
5,510,001 to Hermans et al.; and U.S. Pat. No. 5,510,002 to Hermans
et al.
[0006] As noted in the above, throughdried products tend to exhibit
enhanced bulk and softness. Thermal dewatering with hot air,
however, tends to be energy intensive. Wet-press operations wherein
the webs are mechanically dewatered are preferable from an energy
perspective and are more readily applied to furnishes containing
recycle fiber, which tends to form webs with less permeability than
virgin fiber. Many improvements relate to increasing the bulk and
absorbency of compactively dewatered products, which are typically
dewatered, in part, with a papermaking felt.
SUMMARY OF THE INVENTION
[0007] Fabric-creped products of the present invention typically
include fiber-enriched regions of relatively elevated basis weight
linked together with regions of lower basis weight. Especially
preferred products have a drawable reticulum which is capable of
expanding, that is, increasing in void volume and bulk when drawn
to a greater length. This highly unusual and surprising property is
further appreciated by considering the photomicrographs of FIGS. 1
and 2, as well as the data discussed in the Detailed Description
section hereafter.
[0008] A photomicrograph of the fiber-enriched region of an
undrawn, fabric-creped web is shown in FIG. 1, which is in section
along the MD (left to right in the photo). It is seen that the web
has microfolds transverse to the machine direction, i.e., the
ridges or creases extend in the CD (into the photograph). FIG. 2 is
a photomicrograph of a web similar to that shown in FIG. 1, wherein
the web has been drawn 45%. Here, it is seen that the microfolds
have been expanded, dispersing fiber from the fiber-enriched
regions along the machine direction. Without intending to be bound
by any theory, it is believed that this feature of the invention,
rearrangement or unfolding of the material in the fiber-enriched
regions gives rise to the unique macroscopic properties exhibited
by the material.
[0009] In accordance with one aspect, the present invention
provides a method of making a fabric-creped absorbent cellulosic
sheet including the steps of (a) compactively dewatering a paper
making furnish to form a nascent web having an apparently random
distribution of paper making fiber, (b) applying the dewatered web
having the apparently random distribution to a translating transfer
surface moving at a first speed, and (c) fabric-creping the web
from the transfer surface at a consistency of from about 30 to
about 60 percent utilizing a patterned creping fabric, the creping
step occurring under pressure in the fabric-creping nip defined
between the transfer surface and the creping fabric, wherein the
fabric is traveling at a second speed slower than the speed of the
transfer surface, the fabric pattern, nip parameters, velocity
delta and web consistency being selected such that the web is
creped from the transfer surface and redistributed on the creping
fabric to form a web with a drawable reticulum having a plurality
of regions of different local basis weights including at least (i)
a plurality of fiber enriched regions of high local basis weight,
interconnected by way of (ii) a plurality of lower local basis
weight linking regions. The drawable reticulum of the web is
characterized in that it comprises a cohesive fiber matrix capable
of increasing in void volume when dried and subsequently drawn.
Drawing the web increases the bulk of the web, decreases the
sidedness of the web, and attenuates the fiber enriched regions of
the web.
[0010] The method of making absorbent sheet according to the
invention typically results with a non-random distribution of
fibers in the web, wherein the orientation of fibers in the fiber
enriched regions are biased in the CD. It is apparent from the
photomicrographs appended hereto, that orientation in the CD is
strongest adjacent to the fabric knuckle. The web is typically
characterized in that the fiber enriched regions have a plurality
of micro-folds with fold lines or creases transverse to the machine
direction. Drawing the web in the machine direction expands the
microfolds.
[0011] The inventive process is generally operated at a fabric
crepe of from about 10 to about 100 percent, such as operated at a
fabric crepe of at least about 40 percent. A fabric crepe of at
least about 60 or 80 is preferred in some cases; however, the
process may be operated at a fabric crepe of 100 percent or more,
perhaps even in excess of 125 percent, in some cases.
[0012] In another aspect, the invention provides a method of making
a fabric-creped absorbent cellulosic sheet including the steps of
(a) compactively dewatering a papermaking furnish to form a nascent
web having an apparently random distribution of papermaking fiber
(b) applying the dewatered web having the apparently random fiber
distribution to a translating transfer surface moving at a first
speed (c) fabric-creping the web from the transfer surface at a
consistency of from about 30 to about 60 percent utilizing a
patterned creping fabric, the creping step occurring under pressure
in a fabric creping nip defined between the transfer surface and
the creping fabric, wherein the fabric is traveling at a second
speed slower than the speed of the transfer surface. The fabric
pattern, nip parameters, velocity delta and web consistency are
selected such that the web is creped from the transfer surface and
redistributed on the creping fabric to form a web with a drawable
reticulum having a plurality of interconnected regions of different
local basis weight including at least (i) a plurality of fiber
enriched regions of high local basis weight, interconnected by way
of (ii) a plurality of lower local basis weight linking regions.
The drawable reticulum of the web is characterized in that it
comprises a cohesive fiber matrix capable of increasing void volume
upon dry-drawing. The process further includes (d) applying the web
to a drying cylinder, (e) drying the web on the drying cylinder,
(f) removing the web from the drying cylinder, wherein steps (d),
(e) and (0 are performed so as to substantially preserve the
drawable fiber reticulum, and (g) drawing the dried web.
Preferably, the drying cylinder is a Yankee dryer provided with a
drying hood as is well known in the art. The web may be removed
from the Yankee dryer without substantial creping. While a creping
blade may or may not be used, it may be desirable in some cases to
use a blade, such as a non-metallic blade, to gently assist or to
initiate removal of the web from the Yankee dryer.
[0013] In general, the inventive process is operated at a fabric
crepe of from about 10 to about 100 percent, or even 200 or 300
percent, fabric crepe and a crepe recovery of from about 10 to
about 100 percent. As will be appreciated from the description that
follows, crepe recovery is a measure of the amount of crepe that
has been imparted to the web that has been subsequently pulled out.
The process is operated at a crepe recovery of at least about 20
percent in preferred embodiments, such as operated at a crepe
recovery of at least about 30 percent, 40 percent, 50 percent, 60
percent, 80 percent, or 100 percent.
[0014] Any suitable paper making furnish may be employed to make
the cellulosic sheet according to the present invention. The
process is particularly adaptable for use with secondary fiber
since the process is tolerant to fines. Most preferably, the web is
calendered and drawn on line.
[0015] While any suitable method may be used to draw the web, it is
particularly preferred to draw the web between a first roll
operated at a machine direction velocity greater than the creping
fabric velocity and a second roll operated at a machine direction
velocity greater than the first roll.
[0016] In preferred embodiments, the fabric creped absorbent
cellulosic sheet is dried to a consistency of at least about 90, or
even more preferably, at least 92 percent prior to drawing.
Typically, the web is dried to about 98% consistency when dried
in-fabric.
[0017] Generally speaking, the processing parameters and fabric
creping are controlled such that the ratio of percent decrease in
caliper/percent decrease in basis weight of web is less than about
0.85 upon drawing the web. A value of less than about 0.7 or even
0.6 is more preferred.
[0018] In another aspect, the present invention provides a method
of making a fabric-creped absorbent cellulosic sheet including the
steps of (a) compactively dewatering a papermaking furnish to form
a nascent web having an apparently random distribution of
papermaking fibers, (b) applying the dewatered web having the
apparently random fiber distribution to a translating surface
moving at a first speed, and (c) fabric-creping the web from the
transfer surface at a consistency of from about 30 to about 60
percent utilizing a pattern creping fabric. The creping step occurs
under pressure in a fabric-creping nip defined between the transfer
surface and the creping fabric, wherein the fabric is traveling at
a second speed slower than the speed of the transfer surface. The
fabric pattern, nip parameters, and velocity delta and web
consistency are selected such that the web is creped from the
transfer surface and redistributed on the creping fabric to form a
web with a drawable reticulum having a plurality of interconnected
regions of different local basis weights including at least: (i) a
plurality of fiber enriched regions of high local basis weight,
interconnected by way of (ii) a plurality of lower local basis
weight linking regions. The drawable reticulum of the web is
characterized in that it comprises a cohesive fiber matrix capable
of an increase in void volume upon dry-drawing. The process further
includes the steps of (d) applying the web to a drying cylinder,
(e) drying the web on the drying cylinder, (f) peeling the web from
the drying cylinder, and (g) controlling the takeaway angle from
the drying cylinder, wherein steps (d), (e), (f) and (g) are
performed so as to substantially preserve the drawable fiber
reticulum. The dried web is then drawn to final length.
[0019] The step of controlling the take away angle from the drying
cylinder is carried out utilizing a sheet control cylinder in
preferred embodiments. The sheet control cylinder is disposed
adjacent to the drying cylinder such that the gap between the
surface of the drying cylinder and the surface of the sheet control
cylinder is less than about twice the thickness of the web. In
preferred cases, the sheet control cylinder is disposed such that
the gap between the surface of the drying cylinder and the surface
of the sheet control cylinder is about the thickness of the web or
less. Preferably, the web is calendered and drawn on line after
being peeled from the drying cylinder.
[0020] The web is drawn by any suitable amount, depending on the
desired properties. Generally, the web is drawn by at least about
10 percent, usually, by at least about 15 percent, suitably, by at
least about 30 percent. The web may be drawn by at least about 45
percent or 75 percent or more depending upon the amount of fabric
crepe previously applied.
[0021] Any suitable method may be used in order to draw the web.
One preferred method is to draw the web between a first draw roll
operated at a first machine direction velocity, which is desirably
slightly greater than the creping fabric velocity, and a second
draw roll operated at a machine direction velocity substantially
greater than the velocity of the first draw roll. When using this
apparatus, the web advantageously wraps the first draw roll over an
angle sufficient to control slip, ideally, more than 180 E of its
circumference. Likewise, the web wraps over the second draw roll at
another angle sufficient to control slip, ideally, more than 180 E
of its circumference, as well. In preferred cases, the web wraps
each of the first and second draw rolls over from about 200 E to
about 300 E of their respective circumferences. It is also
preferred that the first and second draw rolls are movable with
respect to each other, such that they are going to be disposed in a
first position for threading and a second position for operation,
one side of the web contacting the first draw roll and the other
side of the web contacting the second draw roll.
[0022] In still a further aspect, the present invention provides a
method of making a fabric-creped absorbent cellulosic sheet
including the steps of (a) compactively dewatering a papermaking
furnish to form a nascent web having an apparently random
distribution of papermaking fiber, (b) applying the dewatered web
having the apparently random fiber distribution to a transfer
surface moving at a first speed, and (c) fabric-creping the web
from the transfer surface at a consistency of from about 30 to
about 60 percent utilizing a pattern creping fabric. The creping
step is carried out under pressure in a fabric-creping nip defined
between the transfer surface and the creping fabric, wherein the
fabric is traveling at the second speed slower than the speed of
the transfer surface. The fabric pattern, nip parameters, velocity
delta, and web consistency are selected such that the web is creped
from the transfer surface and redistributed on the creping fabric
to form a web with a drawable reticulum having a plurality of
interconnected regions of different local basis weight including at
least (i) a plurality of fiber enriched regions of high local basis
weight, interconnected by way of (ii) a plurality of lower local
basis weight linking regions. The drawable reticulum of the web is
characterized in that it includes a cohesive fiber matrix capable
of increasing its void volume upon dry-drawing. The process further
includes the steps of (d) adhering the web to a drying cylinder
with a resinous adhesive coating composition, (e) drying the web on
the drying cylinder, and (f) removing the web from the drying
cylinder. Steps (d), (e) and (0 are performed so as to
substantially preserve the drawable fiber reticulum. After drying,
the web is drawn to its final length.
[0023] The drying cylinder is optionally provided with a resinous
protective coating layer underneath the resinous adhesive coating
composition. The resinous protecting coating layer preferably
includes a polyamide resin, such as a diethyline triamine resin, as
is well known in the art. These resins may be cross-linked by any
suitable means.
[0024] The resinous adhesive coating composition is preferably
rewettable. The process is operated such that it includes
maintaining the adhesive resin coating composition on the drying
cylinder such that the coating provides sufficient wet tack
strength upon transfer of the web to the drying cylinder to secure
the web thereto during drying. The adhesive resin coating
composition is also maintained such that the adhesive coating
composition is pliant when dried such that the web may be removed
from the drying cylinder without a creping blade. In this respect,
"pliant" means that the adhesive resin coating composition does not
harden when dried, or is otherwise maintained in a flexible state,
such that the web may be separated from the drying cylinder without
substantial damage. The adhesive coating composition may include a
polyvinyl alcohol resin and preferably includes at leas one
additional resin. The additional resin may be a polysaccharide
resin, such as a cellulosic resin or a starch.
[0025] In a still further aspect, the invention provides a method
of making a fabric-creped absorbent cellulosic sheet as described
above wherein the web is embossed while it is disposed on the
drying cylinder. After embossing, the web is further dried on the
drying cylinder and removed therefrom. Preferably, the steps of
applying the web to the drying cylinder, embossing the web while it
is disposed on the drying cylinder, drying the web on the drying
cylinder and removing the web from the drying cylinder are
performed so as to substantially preserve the drawable fiber
reticulum. After removal from the drying cylinder, the dried web is
drawn. The web is embossed at the drying cylinder when it has a
consistency of less than about 80 percent, typically, when it has a
consistency of less than 70 percent, and preferably, the web is
embossed when its consistency is less than about 50 percent. In
some cases, it may be possible to emboss the web while it is
applied to the drying cylinder with an embossing surface traveling
in the machine direction at a speed slower than the drying
cylinder. In this embodiment, additional crepe is applied to the
web while it is disposed on the drying cylinder.
[0026] Applied vacuum is useful for increasing CD stretch. Another
method of making a fabric-creped absorbent cellulosic sheet
includes (a) compactively dewatering a papermaking furnish to form
a nascent web having an apparently random distribution of
papermaking fiber, (b) applying the dewatered web having the
apparently random fiber distribution to a translating transfer
surface moving at a first speed, and (c) fabric-creping the web
from the transfer surface at a consistency of from about 30 to
about 60 percent utilizing a creping fabric, the creping step
occurring under pressure in a fabric creping nip defined between
the transfer surface and the creping fabric wherein the fabric is
traveling at a second speed slower than the speed of the transfer
surface. The fabric pattern, nip parameters, velocity delta and web
consistency are selected such that the web is creped from the
transfer surface and redistributed on the creping fabric to form a
web with a drawable reticulum having a plurality of interconnected
regions of different local basis weights including at least (i) a
plurality of fiber enriched regions of high local basis weight,
interconnected by way of (ii) a plurality of lower local basis
weight linking regions. The process also includes (d) applying a
vacuum to the web to increase its CD stretch by at least about 5%
with respect to a like web produced by like means without applied
vacuum after fabric creping. Preferably, the vacuum is applied to
the web while the web is held in the creping fabric, and the
creping fabric is selected to increase the CD stretch when suitable
levels of vacuum are applied to the web. Generally, at least 5
inches Hg of vacuum is applied, more typically, at least 10 inches
Hg of vacuum is applied when so desired. Higher vacuum levels, such
as at least 15 inches Hg, or at least 20 inches Hg or at least 25
inches Hg of vacuum, or more, may be applied.
[0027] Applying vacuum to the web preferably increases the CD
stretch of the web by at least about 5-7.5 percent with respect to
a like web produced by the same means, but without having a vacuum
applied thereto after fabric creping, more preferably, applying a
vacuum to the web increases the CD stretch of the web by at least
about 10 percent with respect to a like web produced by the same
means, without having a vacuum applied thereto after fabric
creping. In still other embodiments, applying a vacuum to the web
increases the CD stretch of the web by at least about 20 percent
with respect to a like web produced by the same means without
having a vacuum applied thereto after fabric creping, at least
about 35 percent with respect to a like web produced by the same
means without having a vacuum applied thereto after fabric creping,
or at least about 50 percent with respect to a like web produced by
the same means without having a vacuum applied thereto after fabric
creping being still more preferred in other cases.
[0028] The jet/wire velocity delta is likewise an important
parameter for making the inventive products. A method of making a
fabric-creped absorbent cellulosic sheet includes (a) applying a
jet of papermaking furnish to a forming wire, the jet having a jet
velocity and the wire moving at a forming wire velocity, the
difference between the jet velocity and the forming wire velocity
being referred to as the jet/wire velocity delta, (b) compactively
dewatering the papermaking furnish to form a nascent web, and (c)
fabric-creping the web from the transfer surface at a consistency
of from about 30 to about 60 percent utilizing a creping fabric,
the creping step occurring under pressure in a fabric creping nip
defined between the transfer surface and the creping fabric,
wherein the fabric is traveling at a second speed slower than the
speed of the transfer surface. The fabric pattern, nip parameters,
velocity delta and web consistency are selected such that the web
is creped from the transfer surface and redistributed on the
creping fabric. The process further includes (d) drying the web,
and (e) controlling the jet/wire velocity delta and fabric creping
step including fabric selection, such that the dry MD/CD tensile
ratio of the dried web is about 1.5 or less. In some cases, it is
preferred to control the jet/wire velocity delta and the fabric
creping step such that the dry MD/CD tensile ratio of the dried web
is about 1-0.75 or less, or about 0.5 or less. The jet/wire
velocity delta may be greater than about 300 fpm, such as greater
than about 350 fmp, or the jet/wire velocity delta to be less than
about 50 fpm. The jet/wire velocity delta may also be less than 0
fpm, such that the forming wire speed exceeds the jet velocity.
[0029] Still yet another method of making a fabric-creped absorbent
cellulosic sheet of the invention includes (a) applying a jet of
papermaking furnish to a forming wire, the jet having a jet
velocity and the wire moving at a forming wire velocity, the
difference between the jet velocity and the forming wire velocity
being referred to as the jet/wire velocity delta, (b) compactively
dewatering the papermaking furnish to form a nascent web, and (c)
fabric-creping the web from the transfer surface at a consistency
of from about 30 to about 60 percent utilizing a creping fabric,
the creping step occurring under pressure in a fabric creping nip
defined between the transfer surface and the creping fabric,
wherein the fabric is traveling at a second speed slower than the
speed of the transfer surface. The fabric pattern, nip parameters,
velocity delta and web consistency are selected such that the web
is creped from the transfer surface and redistributed on the
creping fabric. The process further includes (d) drying the web,
and (e) controlling the jet/wire velocity delta and fabric creping
step including fabric selection such that the dry MD/CD tensile
ratio of the dried web is about 1.5 or less, with the proviso that
the jet/wire velocity delta: (i) is negative or (ii) is greater
than about 350 fpm. The jet/wire velocity delta may be greater than
about 400 fpm, such as greater than about 450 fpm. Typically, the
web has a reticulum with a plurality of interconnected regions of
different local basis weights including at least (i) a plurality of
fiber enriched regions of high local basis weight by way of (ii) a
plurality of lower local basis weight linking regions. In preferred
embodiments, the orientation of fibers in the fiber enriched
regions is biased in the CD.
[0030] Still yet other features and advantages of the invention
will become apparent from the following description and appended
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] The invention is described in detail below with reference to
the drawings, wherein like numerals designate similar parts:
[0032] FIG. 1 is a photomicrograph (120.times.) in section along
the machine direction of a fiber-enriched region of a fabric-creped
sheet which has not been drawn subsequent to fabric creping;
[0033] FIG. 2 is a photomicrograph (120.times.) in section along
the machine direction of a fiber-enriched region of a fabric-creped
sheet of the invention which has been drawn 45% subsequent to
fabric creping;
[0034] FIG. 3 is a photomicrograph (10.times.) of the fabric side
of a fabric-creped web which was dried in the fabric;
[0035] FIG. 4 is a photomicrograph (10.times.) of the fabric side
of a fabric-creped web which was dried in-fabric, then drawn
45%;
[0036] FIG. 5 is a photomicrograph (10.times.) of the dryer side of
the web of FIG. 3;
[0037] FIG. 6 is a photomicrograph (10.times.) of the dryer side of
the web of FIG. 4;
[0038] FIG. 7 is a photomicrograph (8.times.) of an open mesh web
including a plurality of high basis weight regions linked by lower
basis weight regions extending therebetween;
[0039] FIG. 8 is a photomicrograph showing an enlarged detail
(32.times.) of the web of FIG. 7;
[0040] FIG. 9 is a photomicrograph (8.times.) showing the open mesh
web of FIG. 7 placed on the creping fabric used to manufacture the
web;
[0041] FIG. 10 is a photomicrograph showing a web having a basis
weight of 19 lbs/ream produced with a 17% Fabric Crepe;
[0042] FIG. 11 is a photomicrograph showing a web having a basis
weight of 19 lbs/ream produced with a 40% Fabric Crepe;
[0043] FIG. 12 is a photomicrograph showing a web having a basis
weight of 27 lbs/ream produced with a 28% Fabric Crepe;
[0044] FIG. 13 is a surface image (10.times.) of an absorbent
sheet, indicating areas where samples for surface and section
scanning electron micrographs (SEMs) were taken;
[0045] FIGS. 14-16 are surface SEMs of a sample of material taken
from the sheet seen in FIG. 13;
[0046] FIGS. 17 and 18 are SEMs of the sheet shown in FIG. 13 in
section across the MD;
[0047] FIGS. 19 and 20 are SEMs of the sheet shown in FIG. 13 in
section along the MD;
[0048] FIGS. 21 and 22 are SEMs of the sheet shown in FIG. 13 in
section, also along the MD;
[0049] FIGS. 23 and 24 are SEMs of the sheet shown in FIG. 13 in
section across the MD;
[0050] FIG. 25 is a schematic diagram of a paper machine for
practicing the process of the present invention;
[0051] FIG. 26 is a schematic diagram of another paper machine for
practicing the process of the present invention;
[0052] FIG. 27 is a schematic diagram of a portion of still yet
another paper machine for practicing the process of the present
invention;
[0053] FIGS. 28A and 28B are schematic diagrams illustrating an
adhesive and protecting coating for use in connection with the
present invention;
[0054] FIGS. 29A and 29B are schematic diagrams illustrating draw
rolls that can be used in connection with the paper machine of FIG.
27;
[0055] FIG. 30 is a schematic diagram of a portion of another paper
machine provided with an embossing roll that embosses the web while
it is adhered to the Yankee cylinder.
[0056] FIG. 31 is a plot of void volume versus basis weight as webs
are drawn;
[0057] FIG. 32 is a diagram showing the machine direction modulus
of webs of the invention wherein the abscissa have been shifted for
purposes of clarity;
[0058] FIG. 33 is a plot of machine direction modulus versus
percent stretch for products of the present invention;
[0059] FIG. 34 is a plot of caliper change versus basis weight
change for various products of the invention;
[0060] FIG. 35 is a plot of caliper versus applied vacuum for
fabric-creped webs;
[0061] FIG. 36 is a plot of caliper versus applied vacuum for
fabric-creped webs and various creping fabrics;
[0062] FIG. 37 is a plot of TMI Friction values versus draw for
various webs of the invention;
[0063] FIG. 38 is a plot of void volume change versus basis weight
change for various products; and
[0064] FIG. 39 is a diagram showing representative curves of MD/CD
tensile ratio versus jet to wire velocity delta for the products of
the invention, and conventional wet press (CWP) absorbent
sheet.
DETAILED DESCRIPTION
[0065] The invention is described in detail below with reference to
several embodiments and numerous examples. Such a discussion is for
purposes of illustration only. Modifications to particular examples
within the spirit and scope of the present invention, set forth in
the appended claims, will be readily apparent to one of skill in
the art.
[0066] Terminology used herein is given its ordinary meaning
consistent with the exemplary definition set forth immediately
below.
[0067] Throughout this specification and claims, when we refer to a
nascent web having an apparently random distribution of fiber
orientation (or use like terminology), we are referring to the
distribution of fiber orientation that results when known forming
techniques are used for depositing a furnish on the forming fabric.
When examined microscopically, the fibers give the appearance of
being randomly oriented, even though, depending on the jet to wire
speed, there may be a significant bias toward machine direction
orientation making the machine direction tensile strength of the
web exceed the cross-direction tensile strength.
[0068] Unless otherwise specified, "basis weight", BWT, bwt, and so
forth, refers to the weight of a 3000 square foot ream of product.
Consistency refers to percent solids of a nascent web, for example,
calculated on a bone dry basis. "Air dry" means including residual
moisture, by convention, up to about 10 percent moisture for pulp
and up to about 6% for paper. A nascent web having 50 percent water
and 50 percent bone dry pulp has a consistency of 50 percent.
[0069] The term "cellulosic", "cellulosic sheet", and the like, is
meant to include any product incorporating papermaking fiber having
cellulose as a major constituent. "Papermaking fibers" include
virgin pulps or recycle (secondary) cellulosic fibers or fiber
mixes comprising cellulosic fibers. Fibers suitable for making the
webs of this invention include: nonwood fibers, such as cotton
fibers or cotton derivatives, abaca, kenaf, sabai grass, flax,
esparto grass, straw, jute hemp, bagasse, milkweed floss fibers,
and pineapple leaf fibers; and wood fibers, such as those obtained
from deciduous and coniferous trees, including softwood fibers,
such as northern and southern softwood kraft fibers; hardwood
fibers, such as eucalyptus, maple, birch, aspen, or the like.
Papermaking fibers can be liberated from their source material by
any one of a number of chemical pulping processes familiar to one
experienced in the art including sulfate, sulfite, polysulfide,
soda pulping, etc. The pulp can be bleached, if desired, by
chemical means including the use of chlorine, chlorine dioxide,
oxygen, alkaline peroxide, and so forth. The products of the
present invention may comprise a blend of conventional fibers
(whether derived from virgin pulp or recycle sources) and high
coarseness lignin-rich tubular fibers, such as bleached chemical
thermomechanical pulp (BCTMP). "Furnishes" and like terminology
refers to aqueous compositions including papermaking fibers,
optionally, wet strength resins, debonders, and the like, for
making paper products.
[0070] As used herein, the term "comparatively dewatering" the web
or furnish refers to mechanical dewatering by wet pressing on a
dewatering felt, for example, in some embodiments, by use of
mechanical pressure applied continuously over the web surface as in
a nip between a press roll and a press shoe, wherein the web is in
contact with a papermaking felt. The terminology "compactively
dewatering" is used to distinguish processes wherein the initial
dewatering of the web is carried out largely by thermal means as is
the case, for example, in U.S. Pat. No. 4,529,480 to Trokhan and
U.S. Pat. No. 5,607,551 to Farrington et al. noted above.
Compactively dewatering a web thus refers, for example, to removing
water from a nascent web having a consistency of less than 30
percent or so by application of pressure thereto and/or increasing
the consistency of the web by about 15 percent or more by
application of pressure thereto.
[0071] Creping fabric and like terminology refers to fabric or belt
that bears a pattern suitable for practicing the process of the
present invention and preferably, is permeable enough such that the
web may be dried while it is held in the creping fabric. In cases
where the web is transferred to another fabric or surface (other
than the creping fabric) for drying, the creping fabric may have
lower permeability.
[0072] "Fabric side" and like terminology refers to the side of the
web that is in contact with the creping and drying fabric. "Dryer
side" or "can side" is the side of the web opposite to the fabric
side of the web.
[0073] Fpm refers to feet per minute, while consistency refers to
the weight percent fiber of the web.
[0074] Jet/wire velocity delta is the difference in speed between
the headbox jet issuing from a headbox (such as headbox 70, FIGS.
25, 26) and the forming wire or fabric. Jet velocity-wire speed is
typically in fpm. In cases where a pair of forming fabrics are
used, the speed of the fabric advancing the web in the machine
direction is used to calculate jet/wire velocity delta, i.e.,
fabric 54, FIG. 25 or felt 78, FIG. 26, in the case of a
crescent-forming machine. In any event, both forming fabrics are
ordinarily at the same speed.
[0075] A "like" web produced by "like" means refers to a web made
from substantially identical equipment in substantially the same
way, that is, with substantially the same overall crepe, fabric
crepe, nip parameters, and so forth.
[0076] MD means machine direction and CD means cross-machine
direction.
[0077] Nip parameters include, without limitation, nip pressure,
nip length, backing roll hardness, fabric approach angle, fabric
takeaway angle, uniformity, and velocity delta between surface of
the nip.
[0078] Nip length means the length over which the nip surfaces are
in contact.
[0079] The drawable reticulum is "substantially preserved" when the
web is capable of exhibiting a void volume increase upon
drawing.
[0080] "On line" and like terminology refers to a process step
performed without removing the web from the papermachine in which
the web is produced. A web is drawn or calendered on line when it
is drawn or calendered without being severed prior to wind-up.
[0081] "Pliant", in the context of creping adhesive, means that the
adhesive resin coating composition does not harden when dried, or
is otherwise maintained in a flexible state such that the web may
be separated from the drying cylinder without substantial damage.
The adhesive coating composition may include a polyvinyl alcohol
resin, and preferably includes at least one additional resin. The
additional resin may be a polysaccharide resin, such as a
cellulosic resin or a starch.
[0082] A translating transfer surface refers to the surface from
which the web is creped into the creping fabric. The translating
transfer surface may be the surface of a rotating drum as described
hereafter, or may be the surface of a continuous smooth moving belt
or another moving fabric, which may have a surface texture, and so
forth. The translating surface needs to support the web and
facilitate the high solids creping as will be appreciated from the
discussion that follows.
[0083] Calipers and/or bulk reported herein may be measured 1, 4 or
8 sheet calipers as specified. The sheets are stacked and the
caliper measurement taken about the central portion of the stack.
Preferably, the test samples are conditioned in an atmosphere of 23
E.+-.1.0 EC (73.4 E.+-.1.8 EF) at 50% relative humidity for at
least about 2 hours and then measured with a Thwing-Albert Model
89-11-JR or Progage Electronic Thickness Tester with 2-in (50.8-mm)
diameter anvils, 539.+-.10 grams dead weight load, and 0.231
in./sec descent rate. For finished product testing, each sheet of
product to be tested must have the same number of plies as the
product is sold. For testing in general, eight sheets are selected
and stacked together. For napkin testing, napkins are unfolded
prior to stacking. For basesheet testing off of winders, each sheet
to be tested must have the same number of plies as produced off the
winder. For basesheet testing off of the papermachine reel, single
plies must be used. Sheets are stacked together aligned in the MD.
On custom embossed or printed product, try to avoid taking
measurements in these areas if at all possible. Bulk may also be
expressed in units of volume/weight by dividing caliper by basis
weight.
[0084] Absorbency of the inventive products is measured with a
simple absorbency tester. The simple absorbency tester is a
particularly useful apparatus for measuring the hydrophilicity and
absorbency properties of a sample of tissue, napkins, or towel. In
this test, a sample of tissue, napkins, or towel 2.0 inches in
diameter is mounted between a top plastic cover and a bottom
grooved sample plate. The tissue, napkin, or towel sample disc is
held in place by a 1/8 inch wide circumference flange area. The
sample is not compressed by the holder. De-ionized water at 73 EF
is introduced to the sample at the center of the bottom sample
plate through a 1 mm diameter conduit. This water is at a
hydrostatic head of minus 5 mm. Flow is initiated by a pulse
introduced at the start of the measurement by the instrument
mechanism. Water is thus imbibed by the tissue, napkin, or towel
sample from this central entrance point radially outward by
capillary action. When the rate of water imbibation decreases below
0.005 gm water per 5 seconds, the test is terminated. The amount of
water removed from the reservoir and absorbed by the sample is
weighed and reported as grams of water per square meter of sample
or grams of water per gram of sheet. In practice, an M/K Systems
Inc. Gravimetric Absorbency Testing System is used. This is a
commercial system obtainable from M/K Systems Inc., 12 Garden
Street, Danvers, Mass., 01923. WAC or water absorbent capacity,
also referred to as SAT, is actually determined by the instrument
itself WAC is defined as the point where the weight versus time
graph has a "zero" slope, i.e., the sample has stopped absorbing.
The termination criteria for a test are expressed in maximum change
in water weight absorbed over a fixed time period. This is
basically an estimate of zero slope on the weight versus time
graph. The program uses a change of 0.005 g over a 5 second time
interval as termination criteria, unless "Slow SAT" is specified,
in which case, the cut off criteria is 1 mg in 20 seconds.
[0085] Dry tensile strengths (MD and CD), stretch, ratios thereof,
modulus, break modulus, stress and strain are measured with a
standard Instron test device or other suitable elongation tensile
tester, which may be configured in various ways, typically, using 3
or 1 inch wide strips of tissue or towel, conditioned in an
atmosphere of 23 E.+-.1 EC (73.4 E.+-.1 EF) at 50% relative
humidity for 2 hours. The tensile test is run at a crosshead speed
of 2 in/min. Modulus is expressed in lbs/inch per inch of
elongation, unless otherwise indicated.
[0086] Tensile ratios are simply ratios of the values determined by
way of the foregoing methods. Unless otherwise specified, a tensile
property is a dry sheet property.
[0087] "Fabric crepe ratio" is an expression of the speed
differential between the creping fabric and the forming wire, and
is typically calculated as the ratio of the web speed immediately
before fabric creping and the web speed immediately following
fabric creping, the forming wire and transfer surface being
typically, but not necessarily, operated at the same speed:
Fabric crepe ratio=transfer cylinder speed)creping fabric
speed.
[0088] Fabric crepe can also be expressed as a percentage
calculated as:
Fabric crepe, percent=[Fabric crepe ratio-1] H 100%.
[0089] A web creped from a transfer cylinder with a surface speed
of 750 fpm to a fabric with a velocity of 500 fpm has a fabric
crepe ratio of 1.5 and a fabric crepe of 50%.
[0090] The draw ratio is calculated similarly, typically, as the
ratio of winding speed to the creping fabric speed. Draw may be
expressed as a percentage by subtracting 1 from the draw ratio and
multiplying by 100%. The "pullout" or "draw" applied to a test
specimen is calculated from the ratio of final length divided by
its length prior to elongation. Unless otherwise specified, draw
refers to elongation with respect to the length of the as-dried
web. This quantity may also be expressed as a percentage. For
example, a 4'' test specimen drawn to 5'' has a draw ratio of 5/4
or 1.25 and a draw of 25%.
[0091] The total crepe ratio is calculated as the ratio of the
forming wire speed to the reel speed and a % total crepe is:
Total Crepe %=[Total Crepe Ratio-1] H 100%.
[0092] A process with a forming wire speed of 2000 fpm and a reel
speed of 1000 fpm has a line or total crepe ratio of 2 and a total
crepe of 100%.
[0093] The recovered crepe of a web is the amount of fabric crepe
removed when the web is elongated or drawn. This quantity is
calculated as follows and expressed as a percentage:
Recovered Crepe % = 1 - [ % TotalCrepe % FabricCrepe ] .times. 100
% . ##EQU00001##
[0094] A process with a total crepe of 25% and a fabric crepe of
50% has a recovered crepe of 50%.
[0095] Recovered crepe is referred to as the crepe recovery when
quantifying the amount of crepe and draw applied to a particular
web. Sample calculations of the various quantities for a
papermachine 40 of the type shown in FIG. 25 provided with a
transfer cylinder 90, a creping fabric 48, as well as a take up
reel 120, are given in Table 1 below. Recovered fabric crepe is a
product attribute which relates to bulk and void volume as is seen
in the Figures and Examples below.
TABLE-US-00001 TABLE 1 Sample Calculations of Fabric Crepe, Draw
and Recovered Crepe Wire Crepe Fabric Reel TotalCrp fpm fpm fpm
FCRatio FabCrp % % DrawRatio Draw % % Ratio ToCrptPct % RecCrp %
1000 500 750 2.00 100% 1.5 50% 1.33 33% 67% 2000 1500 1600 1.33 33%
1.067 6.7% 1.25 25% 25% 2000 1500 2000 1.33 33% 1.33 33% 1.00 0%
100% 3000 1500 2625 2.00 100% 1.75 75% 1.14 14% 86% 3000 2000 2500
1.50 50% 1.25 25% 1.20 20% 60%
[0096] Friction values and sidedness are calculated by a
modification to the TMI method discussed in U.S. Pat. No. 6,827,819
to Dwiggins et al. This modified method is described below. A
percent change in friction value or sidedness upon drawing is based
on the difference between the initial value without draw and the
drawn value, divided by the initial value, and expressed as a
percentage.
[0097] Sidedness and friction deviation measurements can be
accomplished using a Lab Master Slip & Friction tester, with
special high-sensitivity load measuring option and custom top and
sample support block, Model 32-90 available from: [0098] Testing
Machines Inc. 2910 Expressway Drive South Islandia, N.Y. 11722
www.testingmachines.com adapted to accept a Friction Sensor,
available from: Noriyuki Uezumi Kato Tech Co., Ltd. Kyoto Branch
Office Nihon-Seimei-Kyoto-Santetsu Bldg. 3F Higashishiokoji-Agaru,
Nishinotoin-Dor Shimogyo-ku, Kyotot 600-8216 Japan 81-75-361-6360
katotech@mx1.alpha-web.ne.jp
[0099] The software for the Lab Master Slip and Friction tester is
modified to allow it: (1) to retrieve and directly record
instantaneous data on the force exerted on the friction sensor as
it moves across the samples; (2) to compute an average for that
data; (3) to calculate the deviation-absolute value of the
difference between each of the instantaneous data points and the
calculated mean; and (4) to calculate the mean deviation over the
scan to be reported in grams.
[0100] Prior to testing, the test samples should be conditioned in
an atmosphere of 230.0 E.+-.1 EC (73.4 E.+-.1.8 EF) and 50%.+-.2%
R.H. Testing should also be conducted at these conditions. The
samples should be handled by edges and corners only and any
touching of the area of the sample to be tested should be minimized
as the samples are delicate, and physical properties may be easily
changed by rough handling or transfer of oils from the hands of the
tester.
[0101] The samples to be tested are prepared, using a paper cutter
to get straight edges, as 3-inch wide (CD) by 5-inch long (MD)
strips, any sheets with obvious imperfections being moved and
replaced with acceptable sheets. These dimensions correspond to
those of a standard tensile test, allowing the same specimen to be
first elongated in the tensile tester, then tested for surface
friction.
[0102] Each specimen is placed on the sample table of the tester
and the edges of the specimen are aligned with the front edge of
the sample table and the chucking device. A metal frame is placed
on top of the specimen in the center of the sample table while
ensuring that the specimen is flat beneath the frame by gently
smoothing the outside edges of the sheet. The sensor is placed
carefully on the specimen with the sensor part in the middle of the
sensor holder. Two MD-scans are run on each side of each
specimen.
[0103] To compute the TMI Friction Value of a sample, two MD scans
of the sensor head are run on each side of each sheet, where The
Average Deviation value from the first MD scan of the fabric side
of the sheet is recorded as MD.sub.F1; the result obtained on the
second scan on the fabric side of the sheet is recorded as
MD.sub.F2. MD.sub.D1 and MD.sub.D2 are the results of the scans run
on the Dryer side (Can or Yankee side) of the sheet.
[0104] The TMI Friction Value for the fabric side is calculated as
follows:
TMI_FV F = MD F 1 + MD F 2 2 . ##EQU00002##
[0105] Likewise, the TMI Friction Value for the dryer side is
calculated as:
TMI_FV D = MD D 1 + MD D 2 2 . ##EQU00003##
[0106] An overall Sheet Friction Value can be calculated as the
average of the fabric side and the dryer side, as follows:
TMI_FV AVG = TMI_FV F + TMI_FV D 2 . ##EQU00004##
[0107] Leading to Sidedness as an indication of how much the
friction differs between the two sides of the sheet. The sidedness
is defined as:
Sidedness = TMI_FV U TMI_FV L * TMI_FV AVG . ##EQU00005##
here "U" and "L" subscripts refer to the upper and lower values of
the friction deviation of the two sides (Fabric and Dryer)--that
is, the larger Friction value is always placed in the
numerator.
[0108] For fabric-creped products, the fabric side friction value
will be higher than the dryer side friction value. Sidedness takes
into account not only the relative difference between the two sides
of the sheet, but the overall friction level. Accordingly, low
sidedness values are normally preferred.
[0109] PLI or pli means pounds force per linear inch.
[0110] Pusey and Jones (P&J) hardness (indentation) is measured
in accordance with ASTM D 531, and refers to the indentation number
(standard specimen and conditions).
[0111] Velocity delta means a difference in linear speed.
[0112] The void volume and/or void volume ratio, as referred to
hereafter, are determined by saturating a sheet with a nonpolar
POROFIL.RTM. liquid and measuring the amount of liquid absorbed.
The volume of liquid absorbed is equivalent to the void volume
within the sheet structure. The percent weight increase (PWI) is
expressed as grams of liquid absorbed per gram of fiber in the
sheet structure times 100, as noted hereafter. More specifically,
for each single-ply sheet sample to be tested, select 8 sheets and
cut out a 1 inch by 1 inch square (1 inch in the machine direction
and 1 inch in the cross-machine direction). For multi-ply product
samples, each ply is measured as a separate entity. Multiple
samples should be separated into individual single plies and 8
sheets from each ply position used for testing. Weigh and record
the dry weight of each test specimen to the nearest 0.0001 gram.
Place the specimen in a dish containing POROFIL.RTM. liquid having
a specific gravity of 1.875 grams per cubic centimeter, available
from Coulter Electronics Ltd., Northwell Drive, Luton, Beds,
England; Part No. 9902458. After 10 seconds, grasp the specimen at
the very edge (1-2 Millimeters in) of one corner with tweezers and
remove from the liquid. Hold the specimen with that corner
uppermost and allow excess liquid to drip for 30 seconds. Lightly
dab (less than 1/2 second contact) the lower corner of the specimen
on #4 filter paper (Whatman Lt., Maidstone, England) in order to
remove any excess of the last partial drop. Immediately weigh the
specimen, within 10 seconds, recording the weight to the nearest
0.0001 gram. The PWI for each specimen, expressed as grams of
POROFIL.RTM. liquid per gram of fiber, is calculated as
follows:
PWI=[(W.sub.2-W.sub.1)/W.sub.1] H 100%
wherein
[0113] "W.sub.1" is the dry weight of the specimen, in grams;
and
[0114] "W.sub.2" is the wet weight of the specimen, in grams.
[0115] The PWI for all eight individual specimens is determined as
described above and the average of the eight specimens is the PWI
for the sample.
[0116] The void volume ratio is calculated by dividing the PWI by
1.9 (density of fluid) to express the ratio as a percentage,
whereas the void volume (gms/gm) is simply the weight increase
ratio, that is, PWI divided by 100.
[0117] During fabric creping in a pressure nip, the fiber is
redistributed on the fabric, making the process tolerant of less
than ideal forming conditions, as are sometimes seen with a
Fourdrinier former. The forming section of a Fourdrinier machine
includes two major parts, the headbox and the Fourdrinier Table.
The latter consists of the wire run over the various
drainage-controlling devices. The actual forming occurs along the
Fourdrinier Table. The hydrodynamic effects of drainage, oriented
shear, and the turbulence generated along the table are generally
the controlling factors in the forming process. Of course, the
headbox also has an important influence in the process, usually, on
a scale that is much larger than the structural elements of the
paper web. Thus, the headbox may cause such large-scale effects as
variations in distribution of flow rates, velocities, and
concentrations across the full width of the machine, vortex streaks
generated ahead of and aligned in the machine direction by the
accelerating flow in the approach to the slice, and time-varying
surges or pulsations of flow to the headbox. The existence of
MD-aligned vortices in headbox discharges is common. Fourdrinier
formers are further described in The Sheet Forming Process, Parker,
J. D., Ed., TAPPI Press (1972, reissued 1994) Atlanta, Ga.
[0118] According to the present invention, an absorbent paper web
is made by dispersing papermaking fibers into aqueous furnish
(slurry) and depositing the aqueous furnish onto the forming wire
of a papermaking machine. Any suitable forming scheme might be
used. For example, an extensive, but non-exhaustive list in
addition to Fourdrinier formers, includes a crescent former, a
C-wrap twin wire former, or a suction breast roller former. The
forming fabric an be any suitable foraminous member including
single layer fabrics, double layer fabrics, triple layer fabrics,
photopolymer fabrics, and the like. Non-exhaustive background art
in the forming fabric area includes U.S. Pat. Nos. 4,157,276;
4,605,585; 4,161,195; 3,545,705; 3,549,742; 3,858,623; 4,041,989;
4,071,050; 4,112,982; 4,149,571; 4,182,381; 4,184,519; 4,314,589;
4,359,069; 4,376,455; 4,379,735; 4,453,573; 4,564,052; 4,592,395;
4,611,639; 4,640,741; 4,709,732; 4,759,391; 4,759,976; 4,942,077;
4,967,085; 4,998,568; 5,016,678; 5,054,525; 5,066,532; 5,098,519;
5,103,874; 5,114,777; 5,167,261; 5,199,261; 5,199,467; 5,211,815;
5,219,004; 5,245,025; 5,277,761; 5,328,565; and 5,379,808, all of
which are incorporated herein by reference in their entirety. One
forming fabric particularly useful with the present invention is
Voith Fabrics Forming Fabric 2164 made by Voith Fabrics
Corporation, Shreveport, La.
[0119] Foam-forming of the aqueous furnish on a forming wire or
fabric may be employed as a means for controlling the permeability
or void volume of the sheet upon fabric-creping. Foam-forming
techniques are disclosed in U.S. Pat. No. 4,543,156 and Canadian
Patent No. 2,053,505, the disclosures of which are incorporated
herein by reference. The foamed fiber furnish is made up from an
aqueous slurry of fibers mixed with a foamed liquid carrier just
prior to its introduction to the headbox. The pulp slurry supplied
to the system has a consistency in the range of from about 0.5 to
about 7 weight percent fibers, preferably, in the range of from
about 2.5 to about 4.5 weight percent. The pulp slurry is added to
a foamed liquid comprising water, air and surfactant containing 50
to 80 percent air by volume forming a foamed fiber furnish having a
consistency in the range of from about 0.1 to about 3 weight
percent fiber by simple mixing from natural turbulence and mixing
inherent in the process elements. The addition of the pulp as a low
consistency slurry results in excess foamed liquid recovered from
the forming wires. The excess foamed liquid is discharged from the
system and may be used elsewhere or treated for recovery of
surfactant therefrom.
[0120] The furnish may contain chemical additives to alter the
physical properties of the paper produced. These chemistries are
well understood by the skilled artisan and may be used in any known
combination. Such additives may be surface modifiers, softeners,
debonders, strength aids, latexes, opacifiers, optical brighteners,
dyes, pigments, sizing agents, barrier chemicals, retention aids,
insolubilizers, organic or inorganic crosslinkers, or combinations
thereof; said chemicals optionally comprising polyols, starches,
PPG esters, PEG esters, phospholipids, surfactants, polyamines,
HMCP (Hydrophobically Modified Cationic Polymers), HMAP
(Hydrophobically Modified Anionic Polymers), or the like.
[0121] The pulp can be mixed with strength adjusting agents such as
wet strength agents, dry strength agents and debonders/softeners,
and so forth. Suitable wet strength agents are known to the skilled
artisan. A comprehensive, but non-exhaustive list of useful
strenght aids, includes urea-formaldehyde resins, melamine
formaldehyde resins, glyoxylated polyacrylamide resins,
polyamide-epichlorohydrin resins, and the like. Thermosetting
polyacrylamides are produced by reacting acrylamide with diallyl
ammonium chloride (DADMAC) to produce a cationic polyacrylamide
copolymer, which is ultimately reacted with glyoxal to produce a
cationic cross-linking wet strength resin, glyoxylated
polyacrylamide. These materials are generally described in U.S.
Pat. No. 3,556,932 to Coscia et al. and U.S. Pat. No. 3,556,933 to
Williams et al., both of which are incorporated herein by reference
in their entirety. Resins of this type are commercially available
under the trade name of PAREZ 631NC by Bayer Corporation. Different
mole ratios of acrylamide/-DADMAC/glyoxal can be used to produce
cross-linking resins, which are useful as wet strength agents.
Furthermore, other dialdehydes can be substituted for glyoxal to
produce thermosetting wet strength characteristics. Of particular
utility are the polyamide-epichlorohydrin wet strength resins, an
example of which is sold under the trade names Kymene 557LX and
Kymene 557H by Hercules Incorporated of Wilmington, Del. and
Amres.RTM. from Georgia-Pacific Resins, Inc. These resins and the
processes for making the resins are described in U.S. Pat. No.
3,700,623 and U.S. Pat. No. 3,772,076, each of which is
incorporated herein by reference in its entirety. An extensive
description of polymeric-epihalohydrin resins is given in "Chapter
2: Alkaline-Curing Polymeric Amine-Epicchorohydrin" by Espy in Wet
Strength Resins and Their Application (L. Chan, Editor, 1994),
incorporated herein by reference in its entirety. A reasonably
comprehensive list of wet strength resins is described by Westfelt
in Cellulose Chemistry and Technology Volume 13, p. 813, 1979,
which is incorporated herein by reference.
[0122] Suitable temporary wet strength agents may likewise be
included. A comprehensive, but non-exhaustive, list of useful
temporary wet strength agents includes aliphatic and aromatic
aldehydes including glyoxal, malonic dialdehyde, succinic
dialdehyde, glutaraldehyde and dialdehyde starches, as well as
substituted or reacted starches, disaccharides, polysaccharides,
chitosan, or other reacted polymeric reaction products of monomers
or polymers having aldehyde groups, and optionally, nitrogen
groups. Representative nitrogen containing polymers, which can
suitably be reacted with the aldehyde containing monomers or
polymers, includes vinyl-amides, acrylamides and related nitrogen
containing polymers. These polymers impart a positive charge to the
aldehyde containing reaction product. In addition, other
commercially available temporary wet strength agents, such as PAREZ
745, manufactured by Bayer, can be used, along with those
disclosed, for example, in U.S. Pat. No. 4,605,702.
[0123] The temporary wet strength resin may be any one of a variety
of water-soluble organic polymers comprising aldehydic units and
cationic units used to increase dry and wet tensile strength of a
paper product. Such resins are described in U.S. Pat. Nos.
4,675,394; 5,240,562; 5,138,002; 5,085,736; 4,981,557; 5,008,344;
4,603,176; 4,983,748; 4,866,151; 4,804,769 and 5,217,576. Modified
starches sold under the trademarks CO-BOND.RTM. 1000 and CO-BONDS
1000 Plus, by National Starch and Chemical Company of Bridgewater,
N.J., may be used. Prior to use, the cationic aldehydic water
soluble polymer can be prepared by preheating an aqueous slurry of
approximately 5% solids maintained at a temperature of
approximately 240 degrees Fahrenheit and a pH of about 2.7 for
approximately 3.5 minutes. Finally, the slurry can be quenched and
diluted by adding water to produce a mixture of approximately 1.0%
solids at less than about 130 degrees Farenheit.
[0124] Other temporary wet strength agents, also available from
National Starch and Chemical Company are sold under the trademarks
CO-BOND.RTM. 1600 and CO-BOND.RTM. 2300. These starches are
supplied as aqueous colloidal dispersions and do not require
preheating prior to use.
[0125] Temporary wet strength agents such as glyoxylated
polyacrylamide can be used. Temporary wet strength agents such as
glyoxylated polyacrylamide resins are produced by reacting
acrylamide with diallyl dimethyl ammonium chloride (DADMAC) to
produce a cationic polyacrylamide copolymer, which is ultimately
reacted with glyoxal to produce a cationic cross-linking temporary
or semi-permanent wet strength resin, glyoxylated polyacrylamide.
These materials are generally described in U.S. Pat. No. 3,556,932
to Coscia et al. and U.S. Pat. No. 3,556,933 to Williams et al.,
both of which are incorporated herein by reference. Resins of this
type are commercially available under the trade name of PAREZ
631NC, by Bayer Industries. Different mole ratios of
acrylamide/DADMAC/glyoxal can be used to produce cross-linking
resins, which are useful as wet strength agents. Furthermore, other
dialdehydes can be substituted for glyoxal to produce wet strength
characteristics.
[0126] Suitable dry strength agents include starch, guar gum,
polyacrylamides, carboxylmethyl cellulose, and the like. Of
particular utility is carboxylmethyl cellulose, an example of which
is sold under the trade name Hercules CMC, by Hercules Incorporated
of Wilmington, Del. According to one embodiment, the pulp may
contain from about 0 to about 15 lb/ton of dry strength agent.
According to another embodiment, the pulp may contain from about 1
to about 5 lbs/ton of dry strength agent.
[0127] Suitable debonders are likewise known to the skilled
artisan. Debonders or softeners may also be incorporated into the
pulp or sprayed upon the web after its formation. The present
invention may also be used with softener materials including, but
not limited to, the class of amido amine salts derived from
partially acid neutralized amines. Such materials are disclosed in
U.S. Pat. No. 4,720,383. Evans, Chemistry and Industry, 5 Jul.
1969, pp. 893-903; Egan, J. Am. Oil Chemist's Soc., Vol. 55 (1978),
pp. 118-121; and Trivedi et al., J. Am. Oil Chemist's Soc., June
1981, pp. 754-756, incorporated by reference in their entirety,
indicate that softeners are often available commercially only as
complex mixtures, rather than as single compounds. While the
following discussion will focus on the predominant species, it
should be understood that commercially available mixtures would
generally be used in practice.
[0128] Quasoft 202-JR is a suitable softener material, which may be
derived by alkylating a condensation product of oleic acid and
diethylenetriamine. Synthesis conditions using a deficiency of
alkylation agent (e.g., diethyl sulfate) and only one alkylating
step, followed by pH adjustment to protonate the non-ethylated
species, result in a mixture consisting of cationic ethylated and
cationic non-ethylated species. A minor proportion (e.g., about
10%) of the resulting amido amine cyclize to imidazoline compounds.
Since only the imidazoline portions of these materials are
quaternary ammonium compounds, the compositions as a whole are
pH-sensitive. Therefore, in the practice of the present invention
with this class of chemicals, the pH in the head box should be
approximately 6 to 8, more preferably, 6 to 7 and most preferably,
6.5 to 7.
[0129] Quaternary ammonium compounds, such as dialkyl dimethyl
quaternary ammonium salts are also suitable, particularly, when the
alkyl groups contain from about 10 to 24 carbon atoms. These
compounds have the advantage of being relatively insensitive to
pH.
[0130] Biodegradable softeners can be utilized. Representative
biodegradable cationic softeners/debonders are disclosed in U.S.
Pat. Nos. 5,312,522; 5,415,737; 5,262,007; 5,264,082; and
5,223,096, all of which are incorporated herein by reference in
their entirety. The compounds are biodegradable diesters of
quaternary ammonia compounds, quaternized amine-esters, and
biodegradable vegetable oil based esters functional with quaternary
ammonium chloride and diester dierucyldimethyl ammonium chloride
and are representative biodegradable softeners.
[0131] In some embodiments, a particularly preferred debonder
composition includes a quaternary amine component as well as a
nonionic surfactant.
[0132] The nascent web is typically dewatered on a papermaking
felt. Any suitable felt may be used. For example, felts can have
double-layer base weaves, triple-layer base weaves, or laminated
base weaves. Preferred felts are those having the laminated base
weave design. A wet-press-felt, which may be particularly useful
with the present invention, is Vector 3 made by Voith Fabric.
Background art in the press felt area includes U.S. Pat. Nos.
5,657,797; 5,368,696; 4,973,512; 5,023,132; 5,225,269; 5,182,164;
5,372,876; and 5,618,612. A differential pressing felt, as is
disclosed in U.S. Pat. No. 4,533,437 to Curran et al., may likewise
be utilized.
[0133] Suitable creping fabrics include single layer, multi-layer,
or composite, preferably, open meshed structures. Fabrics may have
at least one of the following characteristics: (1) on the side of
the creping fabric that is in contact with the wet web (the "top"
side), the number of machine direction (MD) strands per inch (mesh)
is from 10 to 200 and the number of cross-direction (CD) strands
per inch (count) is also from 10 to 200; (2) the strand diameter is
typically smaller than 0.050 inch; (3) on the top side, the
distance between the highest point of the MD knuckles and the
highest point on the CD knuckles is from about 0.001 to about 0.02
or 0.03 inch; (4) in between these two levels, there can be
knuckles formed either by MD or CD strands that give the topography
a three dimensional hill/valley appearance which is imparted to the
sheet; (5) the fabric may be oriented in any suitable way so as to
achieve the desired effect on processing and on properties in the
product, the long warp knuckles may be on the top side to increase
MD ridges in the product, or the long shute knuckles may be on the
top side if more CD ridges are desired to influence creping
characteristics as the web is transferred from the transfer
cylinder to the creping fabric; and (6) the fabric may be made to
show certain geometric patterns that are pleasing to the eye, which
is typically repeated between every two to 50 warp yarns. Suitable
commercially available coarse fabrics include a number of fabrics
made by Voith Fabrics.
[0134] The creping fabric may thus be of the class described in
U.S. Pat. No. 5,607,551 to Farrington et al., cols. 7-8 thereof, as
well as the fabrics described in U.S. Pat. No. 4,239,065 to Trokhan
and U.S. Pat. No. 3,974,025 to Ayers. Such fabrics may have about
20 to about 60 filaments per inch and are formed from monofilament
polymeric fibers having diameters typically ranging from about
0.008 to about 0.025 inches. Both warp and weft monofilaments may,
but need not necessarily, be of the same diameter.
[0135] In some cases, the filaments are so woven and
complimentarily serpentinely configured in at least the Z-direction
(the thickness of the fabric) to provide a first grouping or array
of coplanar top-surface-plane crossovers of both sets of filaments,
and a predetermined second grouping or array of sub-top-surface
crossovers. The arrays are interspersed so that portions of the
top-surface-plane crossovers define an array of wicker-basket-like
cavities in the top surface of the fabric, which cavities are
disposed in staggered relation in both the machine direction (MD)
and the cross machine direction (CD), and so that each cavity spans
at least one sub-top-surface crossover. The cavities are discretely
perimetrically enclosed in the plan view by a picket-like-lineament
comprising portions of a plurality of the top-surface plane
crossovers. The loop of fabric may comprise heat set monofilaments
of thermoplastic material, the top surfaces of the coplanar
top-surface-plane crossovers may be monoplanar flat surfaces.
Specific embodiments of the invention include satin weaves as well
as hybrid weaves of three or greater sheds, and mesh counts of from
about 10 H 10 to about 120 H 120 filaments per inch (4 H 4 to about
47 H 47 per centimeter), although the preferred range of mesh
counts is from about 18 by 16 to about 55 by 48 filaments per inch
(9 H 8 to about 22 H 19 per centimeter).
[0136] Instead of an impression fabric, a dryer fabric may be used
as the creping fabric, if so desired. Suitable fabrics are
described in U.S. Pat. No. 5,449,026 (woven style) and U.S. Pat.
No. 5,690,149 (stacked MD tape yarn style) to Lee, as well as U.S.
Pat. No. 4,490,925 to Smith (spiral style).
[0137] If a Fourdrinier former or other gap former is used, the
nascent web may be conditioned with vacuum boxes and a steam shroud
until it reaches a solids content suitable for transferring to a
dewatering felt. The nascent web may be transferred with vacuum
assistance to the felt. In a crescent former, use of a vacuum
assist is unnecessary, as the nascent web is formed between the
forming fabric and the felt.
[0138] Can drying can be used alone or in combination with
impingement air drying, the combination being especially convenient
if a two tier drying section layout is available as hereafter
described. Impingement air drying may also be used as the only
means of drying the web as it is held in the fabric, if so desired,
or either may be used in combination with can dryings. Suitable
rotary impingement air drying equipment is described in U.S. Pat.
No. 6,432,267 to Watson and U.S. Pat. No. 6,447,640 to Watson et
al. Inasmuch as the process of the invention can readily be
practiced on existing equipment with reasonable modifications, any
existing flat dryings can be advantageously employed so as to
conserve capital as well.
[0139] Alternatively, the web may be through-dried after fabric
creping, as is well known in the art. Representative references
include: U.S. Pat. No. 3,432,936 to Cole et al.; U.S. Pat. No.
3,994,771 to Morgan, Jr. et al.; U.S. Pat. No. 4,102,737 to Morton;
and U.S. Pat. No. 4,529,480 to Trokhan.
[0140] Turning to the Figures, FIG. 1 shows a cross section
(120.times.) along the MD of a fabric-creped, undrawn sheet 10
illustrating a fiber-enriched region 12. It will be appreciated
that fibers of the fiber-enriched region 12 have an orientation
biased in the CD, especially, at the right side of region 12, where
the web contacts a knuckle of the creping fabric.
[0141] FIG. 2 illustrates sheet 10 drawn 45% after fabric creping
and drying. Here, it is seen that regions 12 are attenuated or
dispersed in the machine direction when the microfolds of regions
12 expand or unfold. The drawn web exhibits increased bulk and void
volume with respect to an undrawn web. Structural and property
changes are further appreciated by reference to FIGS. 3-12.
[0142] FIG. 3 is a photomicrograph (10.times.) of the fabric side
of a fabric-creped web of the invention that was prepared without
substantial subsequent draw of the web. It is seen in FIG. 3 that
sheet 10 has a plurality of very pronounced high basis weight,
fiber-enriched regions 12 having fiber with orientation biased in
the cross-machine (CD) linked by relatively low basis weight
regions 14. It is appreciated from the photographs that linking
regions 14 have fiber orientation bias extending along a direction
between fiber enriched regions 12. Moreover, it is seen that the
fold lines or creases of the microfolds of fiber enriched regions
12 extend along the CD.
[0143] FIG. 4 is a photomicrograph (10.times.) of the fabric side
of a fabric-creped web of the invention which was fabric creped,
dried and subsequently drawn 45%. It is seen in FIG. 4 that sheet
10 still has a plurality of relatively high basis weight regions 12
linked by lower basis regions 14; however, the fiber-enriched
regions 12 are much less pronounced after the web is drawn, as will
be appreciated by comparing FIGS. 3 and 4.
[0144] FIG. 5 is a photomicrograph (10.times.) of the dryer side of
the web of FIG. 3, that is, the side of the web opposite the
creping fabric. This web was fabric creped and dried without
drawing. Here, there are seen fiber-enriched regions 12 of
relatively high basis weights, as well as lower basis weight
regions 14 linking the fiber-enriched regions. These features are
generally less pronounced on the dryer or "can" side of the web;
except, however, the attenuation or unfolding of the fiber-enriched
regions is perhaps more readily observed on the dryer side of the
web when the fabric-creped web 10 is drawn, as is seen in FIG.
6.
[0145] FIG. 6 is a photomicrograph (10.times.) of the dryer side of
a fabric-creped web 10 prepared in accordance with the invention
which was fabric creped, dried and subsequently drawn 45%. Here, it
is seen that fiber-enriched high basis weight regions 12 "open" or
unfold somewhat as they attenuate (as is also seen in FIGS. 1 and 2
at higher magnification). The lower basis weight regions 14 remain
relatively intact as the web is drawn. In other words, the
fiber-enriched regions are preferentially attenuated as the web is
drawn. It is further seen in FIG. 6 that the relatively compressed
fiber-enriched regions 12 have been expanded in the sheet.
[0146] Without intending to be bound by any theory, it is believed
that fabric-creping the web as described herein produces a cohesive
fiber reticulum having pronounced variation in local basis weight.
The network can be substantially preserved while the web is dried,
for example, such that dry-drawing the web will disperse or
attenuate the fiber-enriched regions somewhat and increase the void
volume of the web. This attribute of the invention is manifested in
FIG. 6 by microfolds in the web at regions 12 opening upon drawing
of the web to a greater length. In FIG. 5, corresponding regions 12
of the undrawn web remain closed.
[0147] The invention process and preferred products thereof are
further appreciated by reference to FIGS. 7 through 24. FIG. 7 is a
photomicrograph of a very low basis weight, open mesh web 20 having
a plurality of relatively high basis weight pileated regions 22
interconnected by a plurality of lower basis weight linking regions
24. The cellulosic fibers of linking regions 24 have an
orientation, which is biased along the direction as to which they
extend between pileated regions 22, as is perhaps best seen in the
enlarged view of FIG. 8. The orientation and variation in local
basis weight is surprising in view of the fact that the nascent web
has an apparently random fiber orientation when formed and is
transferred largely undisturbed to a transfer surface prior to
being wet-creped therefrom. The imparted ordered structure is
distinctly seen at extremely low basis weights where web 20 has
open portions 26 and is thus an open mesh structure.
[0148] FIG. 9 shows a web together with the creping fabric 28 upon
which the fibers were redistributed in a wet-creping nip after
generally random formation to a consistency of 40-50 percent or so
prior to creping from the transfer cylinder.
[0149] While the structure including the pileated and reoriented
regions is easily observed in open meshed embodiments of very low
basis weight, the ordered structure of the products of the
invention is likewise seen when basis weight is increased where
integument regions of fiber 30 span the pileated and linking
regions, as is seen in FIGS. 10 through 12, so that a sheet 32 is
provided with substantially continuous surfaces, as is seen
particularly in FIGS. 19 and 22, where the darker regions are lower
in basis weight, while the almost solid white regions are
relatively compressed fiber.
[0150] The impact of processing variables, and so forth, is also
appreciated from FIGS. 10 through 12. FIGS. 10 and 11 both show a
19 lb sheet; however, the pattern in terms of variation in basis
weight is more prominent in FIG. 11, because the Fabric Crepe was
much higher (40% vs. 17%). Likewise, FIG. 12 shows a higher basis
weight web (27 lb) at 28% crepe where the pileated, linking and
integument regions are all prominent.
[0151] Redistribution of fibers from a generally random arrangement
into a patterned distribution including orientation bias, as well
as fiber-enriched regions corresponding to the creping fabric
structure, is still further appreciated by reference to FIGS. 13
through 24.
[0152] FIG. 13 is a photomicrograph (10.times.) showing a
cellulosic web from which a series of samples was prepared and
scanning electron micrographs (SEMs) made to further show the fiber
structure. On the left of FIG. 13 is shown a surface area from
which the SEM surface images 14, 15 and 16 were prepared. It is
seen in these SEMs that the fibers of the linking regions have an
orientation biased along their direction between pileated regions,
as was noted earlier in connection with the photomicrographs. It is
further seen in FIGS. 14, 15 and 16 that the integument regions
formed have a fiber orientation along the machine direction. The
feature is illustrated rather strikingly in FIGS. 17 and 18.
[0153] FIGS. 17 and 18 are views along line XS-A of FIG. 13, in
section. It is seen especially at 200.times. magnification (FIG.
18) that the fibers are oriented toward the viewing plane, or
machine direction, inasmuch as the majority of the fibers were cut
when the sample was sectioned.
[0154] FIGS. 19 and 20, a section along line XS-B of the sample of
FIG. 13, shows fewer cut fibers, especially at the middle portions
of the photomicrographs, again showing an MD orientation bias in
these areas. Note in FIG. 19, U-shaped folds are seen in the
fiber-enriched area to the left.
[0155] FIGS. 21 and 22 are SEMs of a section of the sample of FIG.
13 along line XS-C. It is seen in these Figures that the pileated
regions (left side) are "stacked up" to a higher local basis
weight. Moreover, it is seen in the SEM of FIG. 22 that a large
number of fibers have been cut in the pileated region (left)
showing reorientation of the fibers in this area in a direction
transverse to the MD, in this case, along the CD. Also noteworthy
is that the number of fiber ends observed diminishes as one moves
from left to right, indicating orientation toward the MD as one
moves away from the pileated regions.
[0156] FIGS. 23 and 24 are SEMs of a section taken along the XS-D
of FIG. 13. Here, it is seen that fiber orientation bias changes as
one moves across the CD. On the left, in a linking or colligating
region, a large number of "ends" are seen indicating MD bias. In
the middle, there are fewer ends as the edge of a pileated region
is traversed, indicating more CD bias until another linking region
is approached and cut fibers again become more plentiful, again
indicating increased MD bias.
[0157] The desired redistribution of fiber is achieved by an
appropriate selection of consistency, fabric or fabric pattern, nip
parameters, and velocity delta, the difference in speed between the
transfer surface and creping fabric. Velocity deltas of at least
100 fpm, 200 fpm, 500 fpm, 1000 fpm, 1500 fpm or even in excess of
2000 fpm may be needed under some conditions to achieve the desired
redistribution of fiber and combination of properties, as will
become apparent from the discussion that follows. In many cases,
velocity deltas of from about 500 fpm to about 2000 fpm will
suffice. Forming the nascent web, for example, control of a headbox
jet and forming wire or fabric speed is likewise important in order
to achieve the desired properties of the product, especially, MD/CD
tensile ratio. Likewise, drying may be carried out while preserving
the drawable reticulum of the web, especially if it is desired to
increase bulk substantially by drawing the web. It is seen in the
discussion that follows that the following salient parameters are
selected or controlled in order to achieve a desired set of
characteristics in the product: consistency at a particular point
in the process (especially at fabric crepe), fabric pattern, fabric
creping nip paramters, fabric crepe ratio, velocity deltas,
especially transfer surface/creping fabric and headbox jet/forming
wire, and post fabric-crepe handling of the web. The products of
the invention are compared with conventional products in Table 2
below.
TABLE-US-00002 TABLE 2 Comparison of Typical Web Properties
Conventional Conventional High Speed Property Wet Press
Throughdried Fabric Crepe SAT g/g 4 10 6-9 *Caliper 40 120+ 50-115
MD/CD Tensile >1 >1 <1 CD Stretch (%) 3-4 7-15 5-15
*mils/8sheet
[0158] FIG. 25 is a schematic diagram of a papermachine 40 having a
conventional twin wire forming section 42, a felt run 44, a shoe
press section 46, a creping fabric 48 and a Yankee drying 50
suitable for practicing the present invention. Forming section 42
includes a pair of forming fabrics 52, 54 supported by a plurality
of rolls 56, 58, 60, 62, 64, 66 and a forming roll 68. A headbox 70
provides papermaking furnish issuing therefrom as a jet in the
machine direction to a nip 72 between forming roll 68 and roll 56
and the fabrics. The furnish forms a nascent web 74, which is
dewatered on the fabrics with the assistance of a vacuum, for
example, by way of vacuum box 76.
[0159] The nascent web is advanced to a papermaking felt 78, which
is supported by a plurality of rolls 80, 82, 84, 85, and the felt
is contact with a shoe press roll 86. The web is a of low
consistency as it is transferred to the felt. Transfer may be
assisted by a vacuum, for example, roll 80 may be a vacuum roll if
so desired or a pickup or vacuum shoe as is known in the art. As
the web reaches the shoe press roll, it may have a consistency of
10-25 percent, preferably, 20 to 25 percent or so as it enters nip
88 between the shoe press roll 86 and transfer roll 90. Transfer
roll 90 may be a heated roll if so desired. Instead of a shoe press
roll, roll 86 could be a conventional suction pressure roll. If a
shoe press is employed, it is desirable and preferred that roll 84
be a vacuum roll effective to remove water from the felt prior to
the felt entering the shoe press nip, since water from the furnish
will be pressed into the felt in the shoe press nip. In any case,
using a vacuum roll at 84 is typically desirable to ensure that the
web remains in contact with the felt during the direction change as
one of skill in the art will appreciate from the diagram.
[0160] Web 74 is wet-pressed on the felt in nip 88 with the
assistance of pressure shoe 92. The web is thus compactively
dewatered at nip 88, typically, by increasing the consistency by 15
or more points at this stage of the process. The configuration
shown at nip 88 is generally termed a shoe press; in connection
with the present invention, cylinder 90 is operative as a transfer
cylinder that operates to convey web 74 at high speed, typically,
1000 fpm-6000 fpm, to the creping fabric.
[0161] Cylinder 90 has a smooth surface 94, which may be provided
with adhesive and/or release agents if needed. Web 74 is adhered to
transfer surface 94 of cylinder 90, which is rotating at a high
angular velocity as the web continues to advance in the
machine-direction, indicated by arrows 96. On the cylinder, web 74
has a generally random apparent distribution of fiber.
[0162] Direction 96 is referred to as the machine-direction (MD) of
the web, as well as that of papermachine 40; whereas the
cross-machine-direction (CD) is the direction in the plane of the
web perpendicular to the MD.
[0163] Web 74 enters nip 88, typically at consistencies of 10-25
percent or so, and is dewatered and dried to consistencies of from
about 25 to about 70 by the time it is transferred to creping
fabric 48, as shown in the diagram.
[0164] Fabric 48 is supported on a plurality of rolls 98, 100, 102
and a press nip roll 104 and forms a fabric crepe nip 106 with
transfer cylinder 90 as shown.
[0165] The creping fabric defines a creping nip over the distance
in which creping fabric 48 is adapted to contact roll 90; that is,
applies significant pressure to the web against the transfer
cylinder. To this end, backing (or creping) roll 100 may be
provided with a soft deformable surface that will increase the
length of the creping nip and increase the fabric creping angle
between the fabric and the sheet, and the point of contact or a
shoe press roll could be used as roll 100 to increase effective
contact with the web in high impact fabric creping nip 106 where
web 74 is transferred to fabric 48 and advanced in the
machine-direction. By using different equipment at the creping nip,
it is possible to adjust the fabric creping angle or the takeaway
angle from the creping nip. Thus, it is possible to influence the
nature and amount of redistribution of fiber,
delamination/debonding which may occur at a fabric creping nip 106
by adjusting these nip parameters. In some embodiments, it may be
desirable to restructure the z-direction interfiber
characteristics; while in other cases, it may be desired to
influence properties only in the plane of the web. The creping nip
parameters can influence the distribution of fiber in the web in a
variety of directions, including inducing changes in the
z-direction, as well as the MD and CD. In any case, the transfer
from the transfer cylinder to the creping fabric is high impact in
that the fabric is traveling slower than the web, and a significant
velocity change occurs. Typically, the web is fabric creped
anywhere from 10-60 percent and higher (200-300%) during transfer
from the transfer cylinder to the fabric.
[0166] Creping nip 106 generally extends over a fabric creping nip
distance of anywhere from about 1/8'' to about 2'', typically,
1/2'' to 2''. For a creping fabric with 32 CD strands per inch, web
74 thus will encounter anywhere from about 4 to 64 weft filaments
in the nip.
[0167] The nip pressure in nip 106, that is, the loading between
backing roll 100 and transfer roll 90 is suitably 20-200,
preferably, 40-70 pounds per linear inch (PLI).
[0168] After fabric creping, the web continues to advance along MD
96 where it is wet-pressed onto Yankee cylinder 110 in transfer nip
112. Transfer at nip 112 occurs at a web consistency of generally
from about 25 to about 70 percent. At these consistencies, it is
difficult to adhere the web to surface 114 of cylinder 110 firmly
enough to remove the web from the fabric thoroughly. This aspect of
the process is important, particularly, when it is desired to use a
high velocity drying hood as well as to maintain high impact
creping conditions.
[0169] In this connection, it is noted that conventional TAD
processes do not employ high velocity hoods, since sufficient
adhesion to the Yankee is not achieved.
[0170] It has been found, in accordance with the present invention,
that the use of particular adhesives cooperate with a moderately
moist web (25-70 percent consistency) to adhere it to the Yankee
sufficiently to allow for high velocity operation of the system and
high jet velocity impingement air drying. In this connection, a
poly(vinyl alcohol)/polyamide adhesive composition, as noted above,
is applied at 116 as needed.
[0171] The web is dried on Yankee cylinder 110, which is a heated
cylinder and by high jet velocity impingement air in Yankee hood
118. As the cylinder rotates, web 74 is creped from the cylinder by
creping doctor 119 and wound on a take-up roll 120. Creping of the
paper from a Yankee dryer may be carried out using an undulatory
creping blade, such as that disclosed in U.S. Pat. No. 5,690,788,
the disclosure of which is incorporated by reference. Use of the
undulatory crepe blade has been shown to impart several advantages
when used in production of soft tissue products. In general, tissue
products creped using an undulatory blade have higher caliper
(thickness), increased CD stretch, and a higher void volume than do
comparable tissue products produced using conventional crepe
blades. All of these changes effected by use of the undulatory
blade tend to correlate with improved softness perception of the
tissue products.
[0172] When a wet-crepe process is employed, an impingement air
dryer, a through-air dryer, or a plurality of can dryers can be
used instead of a Yankee dryer. Impingement air dryers are
disclosed in the following patents and applications, the
disclosures of which are incorporated herein by reference: [0173]
U.S. Pat. No. 5,865,955 to Ilvespaaet et al. [0174] U.S. Pat. No.
5,968,590 to Ahonen et al. [0175] U.S. Pat. No. 6,001,421 to Ahonen
et al. [0176] U.S. Pat. No. 6,119,362 to Sundqvist et al. [0177]
U.S. patent application Ser. No. 09/733,172, entitled Wet Crepe,
Impingement-Air dry Process for Making Absorbent Sheet, now U.S.
Pat. No. 6,432,267. A throughdrying unit is well known in the art
and described in U.S. Pat. No. 3,432,936 to Cole et al., the
disclosure of which is incorporated herein by reference, as is that
of U.S. Pat. No. 5,851,353, which discloses a can-drying
system.
[0178] FIG. 26 shows a preferred papermachine 40 for use in
connection with the present invention. Papermachine 40 is a three
fabric loop machine having a forming section 42 generally referred
to in the art as a crescent former. Forming section 42 includes a
forming wire 52 supported by a plurality of rolls such as rolls 62,
65. The forming section also includes a forming roll 68, which
supports paper making felt 78, such that web 74 is formed directly
on felt 78. Felt run 44 extends to a shoe press section 46, wherein
the moist web is deposited on a transfer roll 90 as described
above. Thereafter, web 74 is creped onto fabric in fabric crepe nip
between rolls 90, 100 before being deposited on Yankee dryer in
another press nip 112. A vacuum is optionally applied by vacuum box
75 as the web is held in fabric. Headbox 70 and press shoe 92
operate as noted above in connection with FIG. 25. The system
includes a vacuum turning roll 84, in some embodiments; however,
the three loop system may be configured in a variety of ways,
wherein a turning roll is not necessary. This feature is
particularly important in connection with the rebuild of a
papermachine, inasmuch as the expense of relocating associated
equipment, i.e., pulping or fiber processing equipment and/or the
large and expensive drying equipment, such as the Yankee dryer or
plurality of can dryers, would make a rebuild prohibitively
expensive, unless the improvements could be configured to be
compatible with the existing facility.
[0179] FIG. 27 schematically shows a portion of a paper machine
200. Paper machine 200 is provided with a forming and fabric
creping section, as described above, wherein a web 205 is
fabric-creped onto a creping fabric 202. Web 205 is transferred
from the creping fabric to a Yankee dryer 206. Rather than being
creped from the Yankee dryer, the web is transferred off the dryer
at sheet control 210. The web is then fed to a pair of draw rolls
212, 214, as described in more detail hereafter. There is
optionally provided a calendering station 216 having a pair of
calender rolls 218 220. Web 205 is thus calendered on line before
being wound onto reel 224 over guide roll 222.
[0180] In order to achieve the advantages of the invention, it is
believed that high fabric crepe ratios should be practiced at the
creping section. The sheet so made may then be attached to a Yankee
dryer as shown generally in FIG. 27, but with a special adhesion
system explained in more detail hereafter. The sheet is preferably
dried to the desired dryness on the Yankee cylinder. Instead of
creping the sheet off the cylinder, a relatively small diameter
control roll 210 is located very close to, and optionally touching,
the Yankee dryer. This relatively smaller diameter roll controls
the sheet pull off angle so that the sheet does not dance up and
down on the dryer surface. The smaller the diameter, the sharper
the take off angle, and the sharper the take off angle, the less
tension is required in the machine direction of the sheet to break
the adhesion of web 205 to Yankee dryer 206. The sheet may
subsequently be taken through a pull out section where a major
portion of the fabric crepe provided to the web in the creping
section is removed from the sheet. This stretching or drawing of
the web opens up the plies of fiber that tend to build up ahead of
the creping knuckle, thereby improving the absorptive properties of
the sheet, as well as the tactile properties. The sheet or web can
then be calendered to reduce two-sidedness and to maintain the
desired caliper properties. As shown in FIG. 27, calendering is
preferably done on line.
[0181] It will be appreciated by those of skill in the art that the
overall process is exceedingly efficient as the wet end may be run
very fast as compared with the Yankee dryer, and the reel can also
be run considerably faster than the Yankee dryer. The slow Yankee
dryer speeds mean that more efficient drying of heavy weight sheets
can be readily achieved with the apparatus of the present
invention. Referring to FIGS. 28A and 28B, a preferred adhesive
system for use with the present invention is schematically shown.
FIG. 28A is a schematic profile of a Yankee dryer, such as a Yankee
dryer 206, wherein an adhesive layer 230 is provided under web 205.
FIG. 28B is an enlarged view showing the various layers of FIGS.
28A. The Yankee dryer surface is indicated as 232, while the web is
indicated at 205. Adhesive layer 230 includes soft adhesive 234, as
well as a dryer protection layer 236.
[0182] For the process of the invention to be operated in preferred
embodiments, the dryer coating should have the following
characteristics.
[0183] Because the sheet has been embedded into the creping fabric
at the creping fabric step, the adhesive needs to exhibit
considerable wet tack properties in order to effectively transfer
the web from the creping fabric to the Yankee dryer. For this
reason, the creping process of the present invention generally
requires an adhesive with high wet tact, such as PVOH, to be used
in the adhesive mix. However, PVOH, while exhibiting high wet tact,
also exhibits very high dry adhesion levels, requiring the use of a
creping blade to remove the dried sheet from the dryer surface. For
the process of FIG. 27 to run, the sheet must be drawn off the
dryer surface without excessively pulling the stretch out of the
sheet, destroying the integrity of the web or breaking the sheet at
defect points. Therefore, this adhesive level, described as soft
adhesive must be aggressive in tacking the wet sheet to the dryer
surface, strong enough in holding the sheet to the dryer under the
influence of high velocity drying hoods, but at the removal point,
the adhesive must exhibit sufficient release characteristics so the
desired sheet properties are preserved. That is to say, the nature
of the drawable fiber reticulum should be preserved. It is believed
that the adhesive must exhibit: high wet tack and low dry adhesion
to the sheet, cohesive internal strength much greater than the
dried paper adhesion strength, so that bits of adhesive do not
leave with the sheet, and very high dry adhesion to the dryer
surface. The dryer protection layer should have very high dry
adhesion to the dryer surface. In normal operations, a creping
blade is required to start the sheet in the winding process before
it can be pulled off the dryer surface. During this time, care must
be taken to prevent the blade from damaging the dryer surface or
removing the adhesive coating. This can be accomplished with the
nature of these coating materials by using a soft, non-metallic
creping blade for sheet starting. The dryer protection layer is
applied and cured prior to the drying being used to dry paper. This
layer can be applied after a dryer grind or after thoroughly
cleaning the old coatings off the dryer surface. This coating is
usually a polyamide based, cross linkable material that is applied
and then cured with heat prior to start up.
[0184] FIGS. 29A and 29B are schematic diagrams showing the
starting and operating configuration of draw rolls 212 and 214. The
draw rolls are mounted on moveable axles at 240 and 242,
respectively. During start up, rolls 212 and 214 are generally
disposed in opposing relationship on either side of web 205. The
configuration shown is particularly convenient for threading web
205. Once threaded, the rolls are rotated upwards of 270E so that
the sheet will wrap around the two rolls sufficiently, so the sheet
can be gripped and pulled out by each of the driven rolls. The
operational configuration is shown in FIG. 29B, where the rolls run
at speeds that are above the speeds of Yankee dryer. Roll 214 is
run at speeds slightly faster than the Yankee dryer, so that the
sheet can be pulled off the Yankee dryer and the stretching process
begun. Roll 212 will run considerably faster than roll 214.
Downstream of this stretch section, may be further provided
calender stations where the remaining pull out will occur between
the calender rolls and roll 212. It is preferable that all of the
rolls are located as closely as is practical, to minimize open
sheet draws as the web progresses in the machine direction.
[0185] Further refinement will be readily appreciated by those of
skill in the art. For example, FIG. 30 shows a paper machine 300
substantially the same as paper machine 200, additionally provided
with an embossing roll 315 provided to emboss the web shortly after
it is applied to the Yankee dryer.
[0186] That is to say, FIG. 30 shows a paper machine 300 including
a conventional forming section, a fabric creping section (not
shown), which includes a creping fabric 302, which carries a web
305 to a Yankee dryer 306. Web 305 is transferred to the surface of
Yankee dryer 306, and shortly thereafter, embossed with an
embossing roll 315 as web 305 is dried. In some cases, when it is
desired to peel the web from the Yankee dryer, it may be preferred
to run the embossing roll and the dryer surface at a slight speed
differential. Preferably, the Yankee dryer 306 is provided with an
adhesive system having a Yankee protection layer and a soft layer
as noted above. The web is dried on the Yankee and removed at
control roll 310. The web is drawn or stretched by draw rolls 312,
314, and then calendered at 316 prior to being rolled up on reel
324.
EXAMPLES 1-8 AND EXAMPLES A-F
[0187] A series of absorbent sheets was prepared with different
amounts of fabric crepe and overall crepe. In general, a 50/50
southern softwood kraft/southern hardwood kraft furnish was used
with a 36 m (M weave with CD knuckles to the sheet). Chemicals such
as debonders and strength resins were not used. The fabric crepe
ratio was about 1.6. The sheet was fabric creped at about 50%
consistency using a line force of about 25 pli against the backing
roll. Thereafter, the sheet was dried in the fabric by bringing it
into contact with heated dryer cans, removed from the fabric and
wound onto the reel of the papermachine. Data from these trials are
designated as Examples 1-8 in Table 3, where post fabric creping
draw is also specified.
[0188] Further trials were made with an apparatus using compactive
dewatering, fabric creping and Yankee drying (instead of can
drying) using an apparatus of the class shown in FIGS. 25 and 26,
wherein the web was adhered to the Yankee cylinder with a polyvinyl
alcohol containing adhesive and removed by blade creping. Data from
these trials appears in Table 3 as Examples A-F.
TABLE-US-00003 TABLE 3 Sheet Properties Examples 1-8; A-F Caliper,
Calc'd Fabric Fabric Opp. Opp. Fric Percent Basis 1 Sheet, Bulk,
Sample Description VV Fric 1 Fric 2 Fric 1 Fric 2 Fric Ratio1
Ratio2 Draw Weight 0.001 in cc/gram 1 Control 5.15 2.379 2.266 2.16
2.74 0 19.6 11.5 9.1 2 15% Draw 5.33 1.402 1.542 1.15 1.53 15 20.1
12.0 9.3 3 30% Draw 5.45 2.016 1.662 1.83 1.27 30 18.4 11.7 9.9 4
45% Draw 6.32 1.843 1.784 1.02 1.78 45 15.3 10.2 10.4 5 Control
1.100 0.828 0 6 15% Draw 1.216 1.011 15 7 30% Draw 1.099 1.304 30 8
45% Draw 1.815 1.002 45 A Control 5.727 1.904 1.730 2.13 1.68 0
21.6 14.2 10.3 B 10% Draw 5.013 2.093 2.003 1.56 1.48 10 20.0 13.2
10.3 C 17% Draw 4.771 0.846 0.818 0.76 0.84 17 19.1 11.4 9.3 D
Control 0.895 1.029 0 14.2 E 10% Draw 1.345 1.356 10 12.7 F 17%
Draw 1.107 0.971 17 11.5
[0189] Without intending to be bound by any theory, it is believed
that if the cohesiveness of the fabric-creped, drawable reticulum
of the web is preserved during drying, then drying the web will
unfold or otherwise attenuate the fiber-enriched regions of the web
to increase absorbency. In Table 4, it is seen that conventional
wet press (CWP) and throughdried products (TAD) exhibit much less
property change upon drawing than fabric creped/can-dried absorbent
sheet of the invention. These results are discussed further below
together with additional examples.
[0190] Following generally the procedures noted above, additional
runs were made with in-fabric (can) dried and Yankee-dried
basesheet. The Yankee-dried material was adhered to a Yankee dryer
with a polyvinyl alcohol adhesive and blade-creped. The
Yankee-dried material generally exhibits less property change upon
drawing (until most of the stretch is pulled out) than did the
can-dried material. This may be altered with less aggressive blade
creping, so that the product behaves more like the can-dried
product. Test data is summarized in Tables 5 and 12 and FIGS. 31
through 39. Fabrics tested included 44G, 44M and 36M oriented in
the MD or CD. Vacuum molding with a vacuum box such as box 75 (FIG.
26) included testing with a narrow 1/4'' and wider 1.5'' slot up to
about 25'' Hg vacuum.
TABLE-US-00004 TABLE 4 Caliper 1 Sheet Void Void Void Void Basis
mils/ Volume Volume Volume Volume Void Volume Weight Example
Description 1 sht Dry Wt g Wet Wt g Wt Inc. % Ratio grams/gram
lbs/3000 ft2 G TAD @ 0 18.8 0.0152 0.1481 873.970 4.600 8.74 14.5 H
TAD @ 10% Pullout 18.5 0.0146 0.1455 900.005 4.737 9.00 13.8 I TAD
@ 15% 17.0 0.0138 0.1379 902.631 4.751 9.03 13.1 J TAD @ 20% 16.2
0.0134 0.1346 904.478 4.760 9.04 12.8 K CWP @ 0 5.2 0.0156 0.0855
449.628 2.366 4.50 14.8 L CWP @ 10% Pullout 5.1 0.0145 0.0866
497.013 2.616 4.97 13.8 M CWP @ 15% 5.0 0.0141 0.0830 488.119 2.569
4.88 13.4 CWP @ 20% 4.6 0.0139 0.0793 472.606 2.487 4.73 13.2
TABLE-US-00005 TABLE 5 Representative Examples 9-34 Caliper After
Initial Void Void Recovery Caliper Void Vol. Vol. Recovered 1 Sheet
1 Sheet Vol. Wet Wt Void Void Stretch (mils/ (mils/ Dry Wt Wt Inc.
Volume Basis Void Original Volume Description (%) 1 sht) 1 sht) (g)
(g) (%) Ratio Weight Volume Caliper Change Yankee-Dried 0 16.5 16.5
0.0274 0.228 732 3.8516 26.0247 7.3180 1.0000 0 16.3 16.3 0.0269
0.221 722 3.7988 25.5489 7.2178 1.0000 15 15.3 16.4 0.0264 0.217
725 3.8162 25.0731 7.2508 0.9329 -0.0023 15 15.4 16.4 0.0264 0.218
726 3.8220 25.1207 7.2619 0.9390 -0.0008 25 13.7 16.5 0.0237 0.200
747 3.9333 22.5040 7.4732 0.8303 0.0283 25 13.6 16.3 0.0240 0.198
725 3.8150 22.7894 7.2485 0.8344 -0.0027 30 12.9 16.6 0.0227 0.191
742 3.9049 21.5524 7.4193 0.7771 0.0208 30 13.0 16.6 0.0227 0.188
732 3.8515 21.5524 7.3178 0.7831 0.0069 35 12.4 16.4 0.0221 0.190
760 3.9987 21.0291 7.5975 0.7561 0.0454 35 12.4 16.4 0.0224 0.189
742 3.9065 21.3145 7.4224 0.7561 0.0213 40 11.6 16.4 0.0213 0.187
782 4.1164 20.2203 7.8212 0.7073 0.0761 40 11.8 16.4 0.0213 0.190
793 4.1760 20.2203 7.9344 0.7195 0.0917 Can-dried 0 12.4 12.4
0.0226 0.132 482 2.5395 21.5048 4.8250 1.0000 0 12.4 12.4 0.0230
0.138 503 2.6478 21.8379 5.0308 1.0000 20 12.6 12.7 0.0202 0.135
568 2.9908 19.2211 5.6826 0.9921 0.1531 20 11.9 12.4 0.0200 0.130
549 2.8884 19.0308 5.4880 0.9597 0.1137 40 11.1 12.2 0.0176 0.129
635 3.3427 16.6996 6.3512 0.9098 0.2888 40 11.1 12.1 0.0177 0.128
621 3.2679 16.8423 6.2091 0.9174 0.2600 45 11.1 12.2 0.0175 0.129
635 3.3399 16.6520 6.3457 0.9098 0.2877 45 11.0 12.1 0.0160 0.121
654 3.4406 15.2247 6.5371 0.9091 0.3265 50 11.1 12.8 0.0168 0.124
641 3.3762 15.9383 6.4147 0.8672 0.3017 50 10.5 12.2 0.0162 0.122
653 3.4364 15.3674 6.5291 0.8607 0.3249 55 10.3 12.1 0.0166 0.125
653 3.4395 15.7480 6.5350 0.8512 0.3261 55 10.0 12.4 0.0165 0.123
651 3.4277 15.6529 6.5126 0.8065 0.3216 60 9.6 12.2 0.0141 0.117
731 3.8463 13.4167 7.3080 0.7869 0.4830 60 9.6 12.5 0.0151 0.116
673 3.5404 14.3207 6.7267 0.7680 0.3650
TABLE-US-00006 TABLE 6 Modulus Data Can-Dried Sheet 7 Point Stretch
Modulus 0.0% 0.1% 0.2% 0.2% 0.3% 0.3% 0.4% 0.4% 2.901 0.5% 0.800
0.6% 6.463 0.6% 8.599 0.7% 7.007 0.7% 9.578 0.8% 10.241 0.8% 9.671
0.9% 8.230 0.9% 8.739 1.0% 11.834 1.1% 11.704 1.1% 7.344 1.2% 4.605
1.2% 5.874 1.3% 9.812 1.3% 7.364 1.4% 7.395 1.4% 3.595 1.5% 9.846
1.6% 9.273 1.6% 9.320 1.7% 9.044 1.7% 8.392 1.8% 6.904 1.8% 9.106
1.9% 4.188 1.9% 9.058 2.0% 5.812 2.1% 6.829 2.1% 8.861 2.2% 8.726
2.2% 7.547 2.3% 8.551 2.3% 5.323 2.4% 8.749 2.4% 8.335 2.5% 3.565
2.6% 7.184 2.6% 10.009 2.7% 6.210 2.7% 4.050 2.8% 6.196 2.8% 6.650
2.9% 3.741 2.9% 4.788 3.0% 1.204 3.1% 4.713 3.1% 6.730 3.2% 1.970
3.2% 6.071 3.3% 9.930 3.3% 1.369 3.4% 6.921 3.4% 4.998 3.5% 3.646
3.6% 8.263 3.6% 1.287 3.7% 2.850 3.7% 4.314 3.8% 3.653 3.8% 4.033
3.9% 3.033 3.9% 2.546 4.0% 2.951 4.1% -1.750 4.1% 3.651 4.2% 3.476
4.2% 1.422 4.3% 2.573 4.3% 2.629 4.4% 0.131 4.4% 7.777 4.5% 2.504
4.6% 0.845 4.6% 4.639 4.7% 2.827 4.7% 1.037 4.8% 4.396 4.8% -0.680
4.9% 3.015 4.9% 4.976 5.0% 2.223 5.1% 2.288 5.1% 1.501 5.2% -0.534
5.2% 3.253 5.3% 1.184 5.3% 0.749 5.4% -0.231 5.4% 0.069 5.5% 2.161
5.6% 6.864 5.6% 1.515 5.7% -0.281 5.7% -2.001 5.8% 2.136 5.8% 4.216
5.9% -0.066 5.9% -0.596 6.0% -0.031 6.1% 1.187 6.1% 1.689 6.2%
1.424 6.2% 1.363 6.3% 3.877 6.3% 0.712 6.4% 1.810 6.4% 2.368 6.5%
1.531 6.6% 1.984 6.6% 0.014 6.7% -4.405 6.7% 1.606 6.8% 2.634 6.8%
-0.467 6.9% 1.865 6.9% -3.493 7.0% 1.088 7.1% 7.333 7.1% -0.900
7.2% -2.607 7.2% 3.199 7.3% 1.892 7.3% 1.306 7.4% 1.063 7.4% -0.836
7.5% 1.785 7.6% 4.308 7.6% -0.647 7.7% 2.090 7.7% 2.956 7.8% -0.666
7.8% 1.187 7.9% -0.059 7.9% -2.503 8.0% 0.420 8.1% -0.130 8.1%
-1.059 8.2% 4.016 8.2% -0.561 8.3% 0.784 8.3% 4.101 8.4% 3.313 8.4%
1.557 8.5% 1.425 8.6% -1.135 8.6% 3.694 8.7% 0.668 8.7% -1.626 8.8%
-0.210 8.8% -0.014 8.9% 2.920 8.9% 3.213 9.0% -0.456 9.1% 3.403
9.1% 2.034 9.2% -1.436 9.2% -2.670 9.3% -0.091 9.3% -1.808 9.4%
1.817 9.4% -1.529 9.5% -1.259 9.6% 4.814 9.6% 3.044 9.7% 2.383 9.7%
0.411 9.8% -1.111 9.8% 1.785 9.9% 2.055 9.9% -0.801 10.0% 0.466
10.1% -0.899 10.1% 0.396 10.2% 2.543 10.2% 0.226 10.3% 1.842 10.3%
-0.704 10.4% 2.350 10.4% 1.707 10.5% 0.120 10.6% 1.741 10.6% 0.553
10.7% -0.931 10.7% -0.635 10.8% 0.713 10.8% 0.040 10.9% 0.645 10.9%
0.111 11.0% 1.532 11.1% 2.753 11.1% 3.364 11.2% -0.970 11.2% -0.717
11.3% 3.049 11.3% -1.919 11.4% 0.342 11.4% 0.354 11.5% -1.510 11.6%
2.085 11.6% 1.217 11.7% -0.780 11.7% 4.265 11.8% -0.565 11.8% 1.150
11.9% 3.509 11.9% 1.145 12.0% 1.268 12.1% 1.923 12.1% -1.835 12.2%
0.943 12.4% 0.581 12.7% 0.634 13.0% 1.556 13.3% 1.290 13.6% 0.467
13.8% 1.042 14.1% 1.116 14.4% 0.339 14.7% 0.869 14.9% -0.213 15.2%
0.192 15.5% 0.757 15.8% 0.652 16.1% 0.648 16.3% 0.461 16.6% 0.142
16.9% 0.976 17.2% 0.958 17.4% 0.816 17.7% 0.180 18.0% 0.318 18.3%
1.122 18.6% 1.011 18.8% 0.756 19.1% 0.292
19.4% 0.257 19.7% 1.411 19.9% 1.295 20.2% 0.467 20.5% 0.858 20.8%
-0.177 21.1% 1.148 21.3% 1.047 21.6% 0.758 21.9% 0.056 22.2% 1.050
22.4% 0.450 22.7% 1.128 23.0% 0.589 23.3% 0.679 23.6% 0.618 23.8%
1.539 24.1% 0.867 24.4% 1.251 24.7% 1.613 24.9% 0.798 25.2% 0.959
25.5% 0.896 25.8% 0.533 26.1% 1.354 26.3% 0.530 26.6% 0.905 26.9%
1.304 27.2% 1.596 27.4% 1.333 27.7% 1.307 28.0% 0.425 28.3% 1.695
28.6% 0.966 28.8% 0.425 29.1% 0.100 29.4% 0.774 29.7% 1.388 29.9%
1.413 30.2% 0.636 30.5% 1.316 30.8% 1.738 31.1% 1.870 31.3% 1.460
31.6% 1.317 31.9% 1.209 32.2% 1.623 32.4% 1.304 32.7% 1.434 33.0%
1.265 33.3% 1.649 33.6% 1.194 33.8% 1.354 34.1% 0.968 34.4% 0.932
34.7% 1.107 34.9% 1.554 35.2% 0.880 35.5% 1.389 35.8% 1.876 36.1%
1.733 36.3% 2.109 36.6% 1.920 36.9% 1.854 37.2% 1.480 37.4% 1.780
37.7% 1.441 38.0% 2.547 38.3% 1.780 38.6% 1.762 38.8% 2.129 39.1%
2.132 39.4% 1.968 39.7% 2.307 39.9% 1.983 40.2% 1.929 40.5% 2.692
40.8% 2.018 41.1% 3.112 41.3% 2.261 41.6% 3.022 41.9% 1.739 42.2%
3.274 42.4% 2.516 42.7% 2.436 43.0% 1.949 43.3% 3.357 43.6% 1.880
43.8% 3.140 44.1% 2.899 44.4% 2.993 44.7% 3.665 44.9% 3.671 45.2%
2.694 45.5% 4.047 45.8% 3.875 46.1% 2.465 46.3% 3.712 46.6% 3.560
46.9% 2.967 47.2% 3.945 47.4% 3.337 47.7% 4.052 48.0% 5.070 48.3%
4.113 48.6% 4.044 48.8% 4.366 49.1% 4.639 49.4% 5.178 49.7% 4.315
49.9% 4.674 50.2% 4.061 50.5% 4.884 50.8% 6.005 51.1% 5.250 51.3%
4.888 51.6% 4.868 51.9% 5.304 52.2% 5.920 52.4% 5.849 52.7% 4.768
53.0% 5.280 53.3% 5.097 53.6% 6.320 53.8% 5.780 54.1% 6.064 54.4%
5.595 54.7% 6.350 54.9% 5.647 55.2% 6.049 55.5% 5.907 55.8% 5.092
56.1% 5.315 56.3% 5.821 56.6% 5.179 56.9% 5.790 57.2% 6.432 57.4%
5.358 57.7% 5.858 57.8% 5.528 58.1% -0.539 58.3% -4.473 58.6%
-7.596 58.8% -16.304 59.1% -19.957 59.3% -27.423 59.6% -24.870
59.8% -24.354 60.1% -26.042 60.2% -33.413 60.3% -33.355 60.4%
-39.617 60.5% -49.495 60.8% -54.166
TABLE-US-00007 TABLE 7 Modulus Data Yankee-Dried Sheet Stretch 7
Point (%) Modulus 0.0% 0.0% 0.1% 0.2% 0.2% 0.3% 0.3% 0.4% 0.4%
-1.070 0.5% 1.632 0.6% -0.636 0.6% 2.379 0.7% -0.488 0.7% -0.594
0.8% 4.041 0.8% 2.522 0.9% -1.569 0.9% 0.684 1.0% -1.694 1.1% 1.769
1.1% 1.536 1.2% -1.383 1.2% -1.222 1.3% 0.462 1.3% 3.474 1.4% 4.228
1.4% -1.074 1.5% 0.133 1.6% -0.563 1.6% 1.659 1.7% 0.430 1.7% 0.204
1.8% -2.271 1.8% 0.536 1.9% 0.850 1.9% 1.918 2.0% 3.341 2.1% 3.455
2.1% 1.837 2.2% 1.079 2.2% 1.027 2.3% 1.637 2.3% 1.999 2.4% 0.340
2.4% 0.744 2.5% 1.202 2.6% 2.405 2.6% 1.714 2.7% -0.616 2.7% -0.934
2.8% -1.307 2.8% 0.976 2.9% 1.584 2.9% 2.162 3.0% 1.594 3.1% 2.895
3.1% 1.606 3.2% 4.526 3.2% 1.075 3.3% 1.206 3.3% 0.414 3.4% 0.611
3.4% -0.006 3.5% 3.757 3.6% -0.541 3.6% 0.524 3.7% -0.531 3.7%
-0.563 3.8% 2.439 3.8% 2.976 3.9% -1.508 3.9% 0.142 4.0% 2.031 4.1%
2.765 4.1% 1.384 4.2% 2.172 4.2% -0.561 4.3% 2.293 4.3% 0.745 4.4%
1.172 4.4% -2.196 4.5% 0.657 4.6% -1.475 4.6% 1.805 4.7% -0.679
4.7% 1.787 4.8% 3.364 4.8% 3.989 4.9% 0.673 4.9% 2.903 5.0% -0.233
5.1% 1.353 5.1% 2.525 5.2% -1.461 5.2% 0.923 5.3% 3.618 5.3% 1.279
5.4% 1.515 5.4% 1.022 5.5% -1.682 5.6% 1.089 5.6% -1.423 5.7%
-0.381 5.7% 0.464 5.8% 3.053 5.8% 1.658 5.9% 4.678 5.9% 3.621 6.0%
1.960 6.1% 1.921 6.1% 0.775 6.2% 1.072 6.2% 1.441 6.3% -1.200 6.3%
0.089 6.4% 2.611 6.4% 2.132 6.5% 0.832 6.6% 0.665 6.6% 3.531 6.7%
2.040 6.7% 0.289 6.8% 0.654 6.8% 2.516 6.9% 2.139 6.9% 1.454 7.0%
-0.256 7.1% 2.056 7.1% 2.278 7.2% 3.943 7.2% 0.398 7.3% 2.336 7.3%
-1.757 7.4% 1.079 7.4% 0.113 7.5% -0.534 7.6% -2.582 7.6% 0.738
7.7% -1.566 7.7% 4.872 7.8% 0.032 7.8% 0.591 7.9% 2.197 7.9% 3.343
8.0% -0.128 8.1% 2.866 8.1% 1.846 8.2% 2.232 8.2% 2.015 8.3% 1.955
8.3% 1.117 8.4% 2.535 8.4% 0.939 8.5% 0.684 8.6% 1.770 8.6% 1.808
8.7% 0.904 8.7% 0.990 8.8% 1.683 8.8% 1.088 8.9% 0.840 8.9% 1.290
9.0% 1.118 9.1% 1.210 9.1% 1.270 9.2% 0.469 9.2% 0.958 9.3% 1.209
9.3% 0.845 9.4% 0.841 9.4% 1.195 9.5% 1.445 9.6% 1.655 9.8% 1.449
10.1% 1.206 10.4% 1.309 10.7% 1.269 10.9% 1.102 11.2% 1.258 11.5%
0.870 11.8% 1.237 12.1% 0.804 12.3% 1.020 12.6% 0.753 12.9% 1.285
13.2% 0.813 13.4% 1.073 13.7% 0.870 14.0% 1.327 14.3% 1.693 14.6%
0.992 14.8% 1.296 15.1% 1.329 15.4% 1.372 15.7% 1.292 15.9% 1.045
16.2% 0.377 16.5% 1.694 16.8% 0.310 17.1% 0.637 17.3% 0.929 17.6%
1.506 17.9% 1.005 18.2% 1.360 18.4% 0.723 18.7% 1.746 19.0% 1.706
19.3% 1.339 19.6% 0.488 19.8% 1.269 20.1% 0.884 20.4% 1.600 20.7%
0.979 20.9% 0.969 21.2% 0.970 21.5% 1.395 21.8% 1.352 22.1% 1.175
22.3% 0.860 22.6% 0.895 22.9% 1.456 23.2% 1.254 23.4% 1.140 23.7%
0.913 24.0% 1.293 24.3% 0.674 24.6% 1.326 24.8% 1.071 25.1% 1.386
25.4% 1.253 25.7% 1.467 25.9% 1.078 26.2% 1.772 26.5% 1.464 26.8%
1.177 27.1% 1.125 27.3% 0.929 27.6% 1.538 27.9% 2.302 28.2% 1.871
28.4% 1.425 28.7% 1.751 29.0% 1.368 29.3% 2.044
29.6% 1.522 29.8% 0.797 30.1% 1.208 30.4% 1.567 30.7% 1.396 30.9%
2.030 31.2% 1.196 31.5% 1.311 31.8% 1.528 32.1% 1.803 32.3% 1.424
32.6% 1.627 32.9% 1.458 33.2% 2.377 33.4% 2.158 33.7% 1.866 34.0%
1.749 34.3% 1.924 34.6% 2.075 34.8% 2.551 35.1% 1.869 35.4% 2.248
35.7% 2.498 35.9% 2.400 36.2% 3.339 36.5% 2.649 36.8% 2.267 37.1%
2.878 37.3% 2.005 37.6% 2.636 37.9% 2.793 38.2% 2.104 38.4% 2.511
38.7% 2.605 39.0% 2.521 39.3% 2.875 39.6% 2.766 39.8% 2.753 40.1%
2.619 40.4% 2.698 40.7% 3.165 40.9% 3.134 41.2% 4.025 41.5% 4.118
41.8% 4.165 42.1% 3.912 42.3% 4.667 42.6% 3.692 42.9% 3.871 43.2%
3.261 43.4% 3.661 43.7% 3.470 44.0% 4.725 44.3% 3.424 44.6% 3.444
44.8% 4.148 45.1% 5.041 45.4% 3.676 45.7% 4.125 45.9% 3.372 46.2%
3.748 46.5% 4.368 46.8% 3.565 46.8% 3.132 47.1% 2.726 47.4% -4.019
47.4% -10.656 47.5% -21.712 47.6% -45.557 47.6% -62.257
TABLE-US-00008 TABLE 8 Caliper Gain Comparison Long Molding Void
Roll Fabric Box Slot Fabric Caliper Basis Tensile Volume Number Vac
Strands to Width. Crepe mils/ Weight GM Cal/Bwt grams/ Count Level
Sheet Inches Ratio 8 sht Lb/3000 ft{circumflex over ( )}2 g/3 in.
cc/gram gram Representative Examples 35-56 7306 0 MD 0.25 1.30
65.18 13.82 718 9.2 7.4 7307 10 MD 0.25 1.30 77.05 13.21 624 11.4
7.6 7308 5 MD 1.50 1.30 68.60 13.51 690 9.9 7.2 7309 10 MD 1.50
1.30 77.70 13.25 575 11.4 6.7 7310 20 MD 0.25 1.30 88.75 13.19 535
13.1 8.2 7311 20 MD 0.25 1.30 91.05 13.24 534 13.4 8.2 7312 20 MD
1.50 1.30 87.73 13.23 561 12.9 8.4 7313 0 MD 1.50 1.33 64.83 13.50
619 9.4 7314 0 MD 1.50 1.30 64.18 13.47 611 9.3 7315 5 MD 0.25 1.30
70.55 13.38 653 10.3 7316 0 MD 0.25 1.15 52.58 13.23 1063 7.7 7317
0 MD 0.25 1.15 53.05 13.12 970 7.9 6.3 7318 5 MD 0.25 1.15 57.40
13.20 1032 8.5 6.5 7319 10 MD 0.25 1.15 62.45 13.01 969 9.4 6.7
7320 5 MD 1.50 1.15 54.65 12.98 1018 8.2 6.0 7321 10 MD 1.50 1.15
62.43 13.02 991 9.3 6.2 7322 20 MD 1.50 1.15 71.40 13.08 869 10.6
7.5 7323 24 MD 0.25 1.15 77.68 13.21 797 11.5 7324 0 MD 0.25 1.15
75.75 23.53 1518 6.3 7325 0 MD 0.25 1.15 78.90 24.13 1488 6.4 7326
0 MD 0.25 1.15 78.40 24.53 1412 6.2 5.8 7327 15 MD 0.25 1.15 83.93
24.09 1314 6.8 6.1 Representative Examples 57-78 7328 10 MD 1.50
1.15 83.18 24.15 1280 6.7 6.2 7329 20 MD 0.25 1.15 88.35 24.33 1316
7.1 6.2 7330 15 MD 1.50 1.15 86.55 24.40 1364 6.9 6.3 7331 24 MD
1.50 1.15 93.03 24.43 1333 7.4 6.4 7332 24 MD 0.25 1.15 93.13 24.62
1264 7.4 6.5 7333 5 MD 0.25 1.15 79.10 24.68 1537 6.2 5.9 7334 0 MD
0.25 1.30 92.00 25.16 779 7.1 7335 0 MD 0.25 1.30 90.98 24.89 1055
7.1 7336 0 MD 0.25 1.30 91.45 24.15 1016 7.4 6.3 7337 5 MD 0.25
1.30 90.13 23.98 1022 7.3 6.5 7338 10 MD 0.25 1.30 94.93 23.92 980
7.7 6.6 7339 5 MD 1.50 1.30 95.23 24.05 1081 7.7 6.6 7340 20 MD
0.25 1.30 103.20 23.43 961 8.6 7341 15 MD 1.50 1.30 99.88 23.60 996
8.2 6.5 7342 20 MD 1.50 1.30 104.83 24.13 934 8.5 7.1 7343 24 MD
0.25 1.30 106.20 23.98 903 8.6 6.7 7344 24 MD 0.25 1.30 111.20
23.93 876 9.1 7345 0 MD 0.25 1.30 92.08 24.44 967 7.3 6.7 7346 15
MD 0.25 1.30 102.90 23.89 788 8.4 7.2 7347 15 MD 0.25 1.15 91.68
24.15 1159 7.4 6.5 7348 0 MD 0.25 1.15 83.98 24.27 1343 6.7 6.5
7349 24 MD 0.25 1.15 96.43 23.91 1146 7.9 6.9 Representative
Examples 79-100 7351 0 CD 0.25 1.15 86.65 24.33 1709 6.9 7352 0 CD
0.25 1.15 87.60 24.62 1744 6.9 5.9 7353 5 CD 0.25 1.15 88.60 24.76
1681 7.0 5.6 7354 15 CD 0.25 1.15 100.58 24.50 1614 8.0 6.2 7355 24
CD 0.25 1.15 100.33 24.44 1638 8.0 6.3 7356 0 CD 1.50 1.15 88.40
24.18 1548 7.1 7357 0 CD 1.50 1.15 87.05 24.12 1565 7.0 7358 24 CD
1.50 1.15 99.30 24.17 1489 8.0 7359 24 CD 0.25 1.15 104.08 24.21
1407 8.4 7360 0 CD 0.25 1.15 91.18 24.13 1415 7.4 6.3 7361 5 CD
0.25 1.15 92.43 24.18 1509 7.4 6.3 7362 15 CD 0.25 1.15 102.15
24.21 1506 8.2 6.7 7363 24 CD 0.25 1.15 104.50 24.58 1476 8.3 6.7
7364 24 CD 0.25 1.30 119.45 24.72 1056 9.4 7365 24 CD 0.25 1.30
123.25 24.46 952 9.8 7366 24 CD 0.25 1.30 124.30 24.62 1041 9.8 7.0
7367 0 CD 0.25 1.30 100.18 24.52 1019 8.0 6.6 7368 15 CD 0.25 1.30
113.95 24.29 1023 9.1 6.8 7369 5 CD 0.25 1.30 106.55 24.56 1106 8.5
6.6 7370 0 CD 0.25 1.30 96.28 24.68 1238 7.6 6.1 7371 5 CD 0.25
1.30 98.80 24.65 1239 7.8 6.1 7372 15 CD 0.25 1.30 109.80 24.64
1110 8.7 6.4 Representative Examples 101-122 7373 24 CD 0.25 1.30
114.65 24.75 1182 9.0 6.6 7376 0 CD 0.25 1.30 70.88 13.32 723 10.4
6.5 7377 5 CD 0.25 1.30 80.48 13.38 629 11.7 7.5 7378 15 CD 0.25
1.30 100.90 13.71 503 14.3 8.9 7379 20 CD 0.25 1.30 112.55 13.87
468 15.8 9.2 7380 20 CD 0.25 1.30 112.60 12.80 345 17.1 9.8 7381 15
CD 0.25 1.30 103.93 12.96 488 15.6 9.1 7382 5 CD 0.25 1.30 91.35
13.06 499 13.6 7.8 7383 0 CD 0.25 1.30 73.03 13.17 613 10.8 8.1
7386 0 CD 0.25 1.15 59.35 13.21 1138 8.8 5.9 7387 5 CD 0.25 1.15
64.35 13.20 1153 9.5 6.1 7388 15 CD 0.25 1.15 77.43 13.22 1109 11.4
6.7 7389 24 CD 0.25 1.15 83.38 13.31 971 12.2 7.4 7390 24 CD 0.25
1.15 87.28 13.20 895 12.9 7.6 7391 15 CD 0.25 1.15 82.58 13.02 935
12.4 7.2 7392 5 CD 0.25 1.15 68.58 12.97 1000 10.3 6.2 7393 0 CD
0.25 1.15 61.40 12.92 952 9.3 6.3 7394 0 CD 0.25 1.15 57.35 12.67
878 8.8 7395 0 CD 0.25 1.15 57.45 12.83 924 8.7 7396 0 CD 0.25 1.15
58.50 13.50 1053 8.4 6.2 7397 5 CD 0.25 1.15 63.75 13.20 1094 9.4
6.5 7398 15 CD 0.25 1.15 79.08 13.95 878 11.0 6.9 Representative
Examples 123-144 7399 24 CD 0.25 1.15 82.50 13.44 811 12.0 6.7 7400
24 CD 0.25 1.30 96.88 13.68 566 13.8 7401 24 CD 0.25 1.30 96.78
13.70 556 13.8 7.9 7402 15 CD 0.25 1.30 91.00 13.75 585 12.9 8.1
7403 5 CD 0.25 1.30 76.03 13.50 633 11.0 6.9 7404 0 CD 0.25 1.30
69.98 13.19 605 10.3 7.2 7405 0 CD 0.25 1.30 96.58 24.55 1091 7.7
7406 0 CD 0.25 1.30 94.05 24.17 1023 7.6 6.4 7407 5 CD 0.25 1.30
93.65 24.41 888 7.5 6.5 7408 15 CD 0.25 1.30 99.13 24.31 1051 7.9
7.0 7409 24 CD 0.25 1.30 104.48 24.47 988 8.3 7.0 7410 24 CD 0.25
1.15 100.38 24.40 1278 8.0 7411 24 CD 0.25 1.15 97.33 24.33 1302
7.8 7412 24 CD 0.25 1.15 96.83 24.73 1311 7.6 7413 24 CD 0.25 1.15
96.00 24.58 1291 7.6 5.9 7414 15 CD 0.25 1.15 91.88 24.41 1477 7.3
6.2 7415 5 CD 0.25 1.15 84.88 24.37 1521 6.8 6.0 7416 0 CD 0.25
1.15 83.60 23.89 1531 6.8 6.1 7417 0 CD 0.25 1.15 85.33 23.72 1310
7.0 6.2 7418 24 CD 0.25 1.15 103.48 24.05 1252 8.4 6.1 7419 24 CD
0.25 1.30 108.75 24.37 979 8.7 7420 24 CD 0.25 1.30 113.00 24.23
967 9.1 7.4 Representative Examples 145-166 7421 0 CD 0.25 1.30
94.43 24.27 954 7.6 6.6 7423 0 MD 0.25 1.30 94.00 24.75 1164 7.4
7424 0 MD 0.25 1.30 93.83 24.41 969 7.5 6.5 7425 5 MD 0.25 1.30
94.55 23.96 1018 7.7 6.8 7426 15 MD 0.25 1.30 110.53 24.17 1018 8.9
6.7 7427 24 MD 0.25 1.30 115.93 24.39 997 9.3 6.9 7428 24 MD 0.25
1.30 122.83 23.86 834 10.0 7429 0 MD 0.25 1.30 95.40 23.88 915 7.8
7430 0 MD 0.25 1.15 78.25 24.15 1424 6.3 7431 0 MD 0.25 1.15 80.30
23.60 1365 6.6 7432 0 MD 0.25 1.15 80.53 23.91 1418 6.6 6.0 7433 5
MD 0.25 1.15 81.50 24.37 1432 6.5 5.9 7434 15 MD 0.25 1.15 94.43
23.84 1349 7.7 6.2 7435 24 MD 0.25 1.15 101.90 24.22 1273 8.2 6.6
7438 0 MD 0.25 1.30 72.53 13.82 475 10.2 7439 0 MD 0.25 1.30 71.63
13.47 478 10.4 7.9 7440 5 MD 0.25 1.30 82.75 13.70 541 11.8 7.7
7441 15 MD 0.25 1.30 102.48 13.77 529 14.5 7.8 7442 24 MD 0.25 1.30
104.23 13.80 502 14.7 8.3 7446 0 MD 0.25 1.30 87.08 24.39 1155 7.0
7447 0 MD 0.25 1.30 88.53 24.41 1111 7.1 7448 5 MD 0.25 1.30 90.60
24.50 1105 7.2 6.5 Representative Examples 167-187 7449 5 MD 0.25
1.30 89.15 24.59 1085 7.1 6.3 7450 15 MD 0.25 1.30 99.03 24.26 1014
8.0 6.8 7451 24 MD 0.25 1.30 106.90 24.54 960 8.5 7.4 7452 24 MD
0.25 1.15 87.23 23.90 1346 7.1 7453 24 MD 0.25 1.15 94.05 23.54
1207 7.8 7.2 7454 15 MD 0.25 1.15 87.38 24.15 1363 7.1 6.2 7455 5
MD 0.25 1.15 79.40 24.27 1476 6.4 5.9 7456 0 MD 0.25 1.15 79.45
23.89 1464 6.5 6.1 7457 0 CD 0.25 1.15 88.00 24.48 1667 7.0 7458 0
CD 0.25 1.15 88.43 24.15 1705 7.1 7459 0 CD 0.25 1.15 87.88 24.32
1663 7.0 6.0 7460 5 CD 0.25 1.15 87.13 24.01 1639 7.1 6.2 7461 15
CD 0.25 1.15 99.50 24.18 1580 8.0 6.7 7462 24 CD 0.25 1.15 107.68
24.58 1422 8.5 7.3 7463 24 CD 0.25 1.30 118.33 25.38 1008 9.1 7464
24 CD 0.25 1.30 123.75 24.57 1056 9.8 7465 24 CD 0.25 1.30 120.00
24.86 1035 9.4 7466 15 CD 0.25 1.30 113.10 24.28 1072 9.1 6.4 7467
15 CD 0.25 1.30 110.25 24.49 1092 8.8 7.2 7468 0 CD 0.25 1.30 97.70
24.38 1095 7.8 6.5 7469 0 CD 0.25 1.30 96.83 23.09 1042 8.2 5.6
TABLE-US-00009 TABLE 9 Caliper Change With Vacuum Fabric Caliper
Fabric Fabric Fabric Basis Crepe @ 25 in Ct Type Orientation Weight
Ratio Slope Intercept Hg 44 M MD 13 1.15 1.0369 51.7 77.6 44 G CD
13 1.15 1.1449 57.9 86.6 44 M CD 13 1.15 1.1464 59.8 88.4 44 M MD
13 1.30 1.3260 64.0 97.1 44 G CD 13 1.30 1.1682 70.5 99.7 44 G MD
13 1.30 1.5370 73.2 111.6 44 M CD 13 1.30 1.9913 72.6 122.4 36 M MD
24 1.15 0.5189 78.4 91.4 44 M MD 24 1.15 0.6246 78.2 93.8 44 G CD
24 1.15 0.6324 83.3 99.2 44 G MD 24 1.15 0.9689 78.9 103.1 44 M CD
24 1.15 0.6295 88.1 103.8 36 M CD 24 1.15 0.8385 86.7 107.7 44 M MD
24 1.30 0.6771 90.2 107.1 36 M MD 24 1.30 0.8260 86.6 107.2 44 G CD
24 1.30 0.5974 93.5 108.4 44 G MD 24 1.30 1.1069 92.7 120.4 44 M CD
24 1.30 0.9261 97.6 120.7 36 M CD 24 1.30 0.9942 96.7 121.6
TABLE-US-00010 TABLE 10 Void Volume Change With Vacuum Fabric VV @
Fabric Fabric Fabric Basis Crepe 25 in Ct Type Orientation Weight
Ratio Slope Intercept Hg 44 G CD 13 1.15 0.0237 6.3 6.9 44 M CD 13
1.15 0.0617 6.0 7.5 44 M MD 13 1.15 0.0653 6.0 7.6 44 G MD 13 1.30
0.0431 7.0 8.1 44 G CD 13 1.30 0.0194 7.7 8.2 44 M MD 13 1.30
0.0589 7.0 8.4 44 M CD 13 1.30 0.1191 7.1 10.1 44 G CD 24 1.15
-0.0040 6.1 6.0 44 M MD 24 1.15 0.0204 6.0 6.5 44 G MD 24 1.15
0.0212 6.0 6.5 44 G CD 24 1.15 0.0269 5.9 6.6 36 M MD 24 1.15
0.0456 5.8 7.0 36 M CD 24 1.15 0.0539 5.9 7.3 44 M CD 24 1.30
0.0187 6.3 6.8 44 G MD 24 1.30 0.0140 6.6 6.9 44 M MD 24 1.30
0.0177 6.5 6.9 36 M CD 24 1.30 0.0465 6.1 7.2 44 G CD 24 1.30
0.0309 6.5 7.3 36 M MD 24 1.30 0.0516 6.1 7.4
TABLE-US-00011 TABLE 11 CD Stretch Change With Vacuum Fabric
Stretch Fabric Fabric Fabric Basis Crepe @ 25 Ct Type Orientation
Weight Ratio Slope Intercept in Hg 44 M MD 13 1.15 0.0582 4.147 5.6
44 G CD 13 1.15 0.0836 4.278 6.4 44 G CD 13 1.30 0.0689 6.747 8.5
44 M MD 13 1.30 0.1289 6.729 10.0 44 G MD 13 1.30 0.0769 8.583 10.5
36 M MD 24 1.15 0.0279 4.179 4.9 44 M MD 24 1.15 0.0387 4.526 5.5
44 G MD 24 1.15 0.0534 4.265 5.6 36 M MD 24 1.30 0.0634 5.589 7.2
44 G MD 24 1.30 0.0498 6.602 7.8 44 M MD 24 1.30 0.0596 6.893
8.4
TABLE-US-00012 TABLE 12 TMI Friction Data TMI Friction TMI Friction
Stretch Top Bottom Fabric (%) (Unitless) (Unitless) Yankee- 0 0.885
1.715 Dried 0 1.022 1.261 15 0.879 1.444 15 0.840 1.235 25 1.237
1.358 25 0.845 1.063 30 1.216 1.306 30 0.800 0.844 35 1.221 1.444
35 0.871 1.107 40 0.811 0.937 40 1.086 1.100 Can- 0 0.615 3.651
Dried 0 0.689 1.774 20 0.859 2.100 20 0.715 2.144 40 0.607 2.587 40
0.748 2.439 45 0.757 3.566 45 0.887 2.490 50 0.724 2.034 50 0.929
2.188 55 0.947 1.961 55 1.213 1.631 60 0.514 2.685 60 0.655
2.102
[0191] It is seen in FIG. 31 that the can-dried materials exhibit
more void volume gain as the basis weight is reduced when the sheet
was drawn. Moreover, the Yankee-dried and blade-creped material did
not exhibit any significant void volume gain until relatively large
elongation.
[0192] In Table 6 and Table 7, as well as FIGS. 32 and 33, it is
seen that can-dried material and Yankee-dried material exhibit
similar stress/strain behavior; however, the can-dried material has
a higher initial modulus, which may be beneficial to runnability.
Modulus is calculated by dividing the incremental stress (per inch
of sample width) in lbs by the additional elongation observed.
Nominally, the quantity has units lbs/in.sup.2.
[0193] FIG. 34 is a plot of caliper versus basis weight as the
product is drawn. The Yankee-dried, aggressively creped web
exhibited approximately 1:1 loss of caliper with basis weight
(i.e., approximately constant bulk), whereas the can-dried web lost
much more basis weight than caliper. This result is consistent with
the data set of Examples 1-8, and with the void volume data. The
ratio of percent decrease in basis weight may be calculated and
compared for the different processes. The Yankee-dried material has
an undrawn basis weight of about 26 lbs and a caliper loss of about
28% when drawn to a basis weight of about 20.5; that is, the
material has only about 72% of its original caliper. The basis
weight loss is about 5.5/26 or 21%; thus, the ratio of percent
decrease in caliper/percent decrease in basis weight is
approximately 28/21 or 1.3. It is seen in FIG. 34 that the
can-dried material loses caliper much more slowly with basis weight
reduction as the material is drawn. As the can-dried sheet is drawn
from a basis weight of about 22 lbs to about 14 lbs, only about 20%
of the caliper is lost; and the ratio of % decrease in
caliper/percent decrease in basis weight is about 20/36 or
0.55.
[0194] Results for Yankee-dried and can-dried material upon drawing
is summarized graphically in FIG. 35. It is again seen here that
the caliper of the can-dried material changes less than that of the
Yankee-dried material as the basis weight is reduced. Moreover,
large changes in void volume are observed when the can-dried
material is drawn.
[0195] In FIG. 36, it is seen that caliper is influenced by
selection of vacuum and creping fabric; while Table 12 and FIG. 37
show that the in-fabric can-dried material exhibited much higher
TMI Friction values. In general, friction values decrease as the
material is drawn. It will be appreciated from the data in Table 12
and FIG. 37 that even though samples were run only in the MD, that
as the samples were drawn, the friction values on either side of
the sheet converge; for example, the can-dried samples had average
values of 2.7/0.65 fabric side/can side prior to drawing and
average values of 1.8/1.1 at 55% draw.
[0196] Differences between products of the invention and
conventional products are particularly appreciated by reference to
Table 4 and FIG. 38. It is seen that conventional through dried
(TAD) products do not exhibit substantial increases in void volume
(<5%) upon drawing, and that the increase in void volume is not
progressive beyond 7% draw; that is, the void volume does not
increase significantly (less than 1%) as the web is drawn beyond
10%. The conventional wet press (CWP) towel tested exhibited a
modest increase in void volume when drawn to 10% elongation;
however, the void volume decreased at more elongation, again not
progressively increasing. The products of the present invention
exhibited large, progressive increases in void volume as they are
drawn. Void volume increases of 20%, 30%, 40% and more are readily
achieved.
[0197] Further differences between the inventive processes and
products and conventional products and processes are seen in FIG.
39. FIG. 39 is a plot of MD/CD tensile ratio (strength at break)
versus the difference between headbox jet velocity and forming wire
speed (fpm). The upper U-shaped curve is typical of conventional
wet-press absorbent sheet. The lower, broader curve is typical of
fabric-creped products of the invention over a wide range of jet to
wire velocity deltas, a range that is more than twice that of the
CWP curve shown. Thus, control of the headbox jet/forming wire
velocity delta may be used to achieve desired sheet properties.
[0198] It is also seen from FIG. 39 that MD/CD ratios below square
(i.e., below 1) are difficult, if not impossible, to obtain with
conventional processing. Furthermore, square or below sheets are
formed by way of the invention without excessive fiber aggregates
or "flocs," which is not the case with the CWP products having low
MD/CD tensile ratios. This difference is due, in part, to the
relatively low velocity deltas required to achieve low tensile
ratios in CWP products, and may be due in part to the fact that
fiber is redistributed on the creping fabric when the web is creped
from the transfer surface in accordance with the invention.
Surprisingly, square products of the invention resist propagation
of tears in the CD and exhibit a tendency to self-healing. This is
a major processing advantage, since the web, even though square,
exhibits reduced tendency to break easily when being wound.
[0199] In many products, the cross machine properties are more
important than the MD properties, particularly, in commercial
toweling where CD wet strength is critical. A major source of
product failure is "tabbing" or tearing off only a piece of towel
rather than the entirety of the intended sheet. In accordance with
the invention, CD tensiles may be selectively elevated by control
of the headbox to forming wire velocity delta and fabric
creping.
[0200] While the invention has been described in connection with
several examples, modifications to those examples within the spirit
and scope of the invention will be readily apparent to those of
skill in the art. In view of the foregoing discussion, relevant
knowledge in the art and references including copending
applications discussed above in connection with the Background and
Detailed Description, the disclosures of which are all incorporated
herein by reference, further description is deemed unnecessary.
* * * * *
References